Answer:
add up the mass of protons and neutrons
Explanation:
Answer:
To find the mass number of an element you add up the number of protons (atomic number) and neutrons.Explanation:
The mass number is a specific property of the atoms, defined as the sum of the protons and neutrons, which are the subatomic particles that are in the nucleus of the atom.
The electrons do not count for the mass of atoms because their mass is about 1/1840 the mass of a proton or a neutron.
The relative masses of protons and neutrons is 1: 1, then they count equally.
As an example, the mass number of the atom carbon-12 is calculated in this way:
Atomic number of carbon: Z = 6 (6 protons)Number of neutrons: N = 6Mass number: A = Z + N = 6 + 6 = 12.The number 12 added to the name in carbon-12, stands for its mass number.
Also, the mass number is indicated as a superscript to the left of the chemical symbol of the element, and the atomic number as a subscript to the left of the chemical symbol. For the example of carbon-12 that is:
[tex]^{12}_{6}C[/tex]When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes _____.
A) hydrolyzed
B) oxidized
C) reduced
D) an oxidizing agent
Answer:
B) oxidized
Explanation:
When glucose loses a hydrogen atom, it is losing 1 proton and 1 electron. This loss of an electron means it is oxidized.
The glucose molecule becomes oxidized when it loses a hydrogen atom in an oxidation-reduction reaction. This reflects the loss of electrons, which is characteristic of oxidation, while gaining electrons, or hydrogen atoms, indicates reduction.(Option b)
Explanation:When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes oxidized. This loss of hydrogen represents the molecule giving up electrons, which characterizes the process of oxidation. Conversely, when a molecule gains hydrogen atoms, it is said to be reduced.
In the context of glucose metabolism, an oxidizing agent would be a molecule like NAD+ or FAD, which accepts the electrons that are lost when glucose is oxidized. Hence, the carbohydrate is oxidized, liberating energy that the body can use.
Remember that in the process of cellular respiration, glucose is oxidized into carbon dioxide (CO2), and the oxygen is reduced while forming water (H2O). Glucose losing hydrogens means it is becoming oxidized, and the gaining of hydrogen by oxygen to form water indicates that oxygen is being reduced.
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• 1 mol of beryllium • 1 mol of salt • 1 mol of water • 1 mol of hydrogen Which statement is true about these substances?
Answer:
they all contain the same number of molecules at constant temperature and pressure
Answer:
Option D is correct! - They have different masses.
Explanation:
What caused the different pH values for the test solutions? Each solution has a different concentration of ions. hydroxide or hydrogen?
Answer: The correct answer is hydrogen.
Explanation:
pH is defined as the negative logarithm of hydrogen or hydronium ion concentration that are present in a solution.
The equation representing pH of the solution follows:
[tex]pH=-\log[H^+][/tex]
pH range of the solution varies from 0 to 14.
If the pH of the solution is from 0 to 6.9, the solution is said to be acidic.
If the pH of the solution is from 7.1 to 14, the solution is said to be basic.
If the pH of the solution is 7, the solution is said to be neutral.
Thus, different concentration of hydrogen ions will give us different values of pH.
Hence, the correct answer is hydrogen.
The different pH values for the test solutions result from the distinct concentrations of hydrogen (H+) or hydroxide (OH-) ions present in each solution. Acidic solutions have more H+ ions and a lower pH, while alkaline solutions have more OH- ions and a higher pH.
Explanation:The different pH values for the test solutions are caused by the varying concentrations of their hydrogen ions (H+) or hydroxide ions (OH-). The pH value is essentially a measure of the hydrogen ion concentration in the solution. Acidic solutions have a higher concentration of H+ ions and therefore a lower pH value (below 7), while basic or alkaline solutions have a higher concentration of hydroxide ions, resulting in pH values above 7. For instance, if one solution has more hydroxide ions than another, it will have a higher pH value, indicating it is more basic.
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Match the following.
1. hybrid BB
2. dominant "pure breed" 3:1
3. recessive alleles Bb
4. phenotype ratio bb
Answer:
hybrid BB
Dominant Bb
recessive alleles bb
phenotype ratio 3:1
Answer:
hybrid BB
dominant Bb
recessive alleles bb
phenotype ratio 3:1
Explanation:
because phenotype ratio is a type of ratio so it match with the ratio. that's what l think
The pictured compound has which of the following bonds?
Answer: There are C - C bonds and C - H bonds.
trust me! I took a test with this question and got 100! :)
The pictured compound has C - C bonds and C - H bonds.
What is a Bond?
This is defined as an attraction between atoms, ions or molecules which results in the formation of chemical compounds.
The compound is an alkane as the formula is C₄H₁₀(butane) which has only C - C bonds and C - H bonds single bonds thereby making option C the most appropriate choice.
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Use the measurements in the table to determine which unidentified metal has the highest density.
Metal Volume Mass
A 10.5 cm3 122 g
B 14.2 cm3 132 g
C 16.1 cm3 115 g
D 12.7 cm3 126 g
Answer:
Metal A has the highest density.
Explanation:
Density is defined as mass present in unit volume of the substance.
[tex]Density=\frac{Mass}{Volume}[/tex]
Density of metal A
Mass of metal = 122 g
Volume of metal = [tex]10.5 cm^3[/tex]
[tex]D=\frac{122 g}{10.5 cm^3}=11.61 g/cm^3[/tex]
Density of metal B
Mass of metal = 132 g
Volume of metal = [tex]14.2 cm^3[/tex]
[tex]D=\frac{132 g}{14.2 cm^3}=9.29 g/cm^3[/tex]
Density of metal C
Mass of metal = 115 g
Volume of metal = [tex]16.1 cm^3[/tex]
[tex]D=\frac{115 g}{16.1 cm^3}=7.14 g/cm^3[/tex]
Density of metal D
Mass of metal = 126 g
Volume of metal = [tex]12.7 cm^3[/tex]
[tex]D=\frac{126 g}{12.7 cm^3}=9.92 g/cm^3[/tex]
Metal A has the highest density.
Compared with the freezing-point depression of a 0.01 m c6h12o6 solution, the freezing-point depression of a 0.01 m nacl solution is
Answer:
Twice as much.
Explanation:
That's because the freezing point depression depends on the total number of solute particles.
C₆H₁₂O₆(s) ⟶ C₆H₁₂O₆(aq)
0.01 mol of C₆H₁₂O₆ gives 0.01 mol of solute particles.
NaCl(s) ⟶ Na⁺(aq) + Cl⁻(aq)
1 mol of NaCl gives 0.01 mol of Na⁺(aq) and 0.01 mol of Cl⁻(aq).
That's 0.02 mol of particles, so the freezing point depression of 0.01 mol·L⁻¹ NaCl will be twice that of 0.01 mol·L⁻¹ C₆H₁₂O₆.
Diversification is most effective when security returns are _________.
Answer:
negatively correlated
300 moles of sodium nitrite are needed for a reaction. the solution is 0.450 m. how many ml are needed?
In order to provide the 300 moles of sodium nitrite required for the reaction using a 0.450 m solution, you would need 666,667 mL of the solution.
Explanation:To determine how many milliliters of a 0.450 m sodium nitrite solution are needed for a reaction where 300 moles of sodium nitrite are needed, you'll want to use the equation that relates moles, molarity (M), and volume (V). This equation is Moles = Molarity x Volume.
For the given question, we know the amount of moles (300 moles) and the molarity (0.450 m), so we can rearrange the equation and plug in our values to find the volume: Volume (L) = Moles / Molarity = 300 moles / 0.450 M = 666.67 L.
Do remember to convert this volume to milliliters because the question asks for the answer in milliliters. 666.67 L x 1000 mL/L= 666,667 mL.
Therefore, you would need 666,667 mL of a 0.450 m sodium nitrite solution to provide the 300 moles of sodium nitrite required for the reaction.
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To determine the volume of solution needed for the reaction, we can use the formula Volume = Number of moles / Molarity. In this case, the volume of solution needed is approximately 666,666.67 mL.
Explanation:To determine the volume of solution needed, we need to first calculate the number of moles of sodium nitrite in 300 moles. Since the solution is 0.450 M, this means there are 0.450 moles of sodium nitrite in every 1 liter of solution. Therefore, to calculate the volume of solution needed, we can use the formula:
Volume (in liters) = Number of moles / Molarity
Volume = 300 moles / 0.450 moles
To convert the volume from liters to milliliters, we can multiply the volume by 1000:
Volume (in milliliters) = Volume (in liters) * 1000
Plugging in the values, we get:
Volume (in milliliters) = (300 moles / 0.450 moles) * 1000 = 666666.67 mL
Therefore, approximately 666,666.67 mL of solution are needed for the reaction.
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PLEASE HELP WILL GIVE BRAINLYIST TO FIRST PERSON
Which would have a lower pH, a 0.1 M solution of a strong base or a weak base? Why?
Which would have a higher pH, a 0.1 M solution of a strong acid, or a weak acid? Why?
Answer:
1) Weak base.
2) Weak acid.
Explanation:
1) Which would have a lower pH, a 0.1 M solution of a strong base or a weak base? Why?
For bases:Solution with lower pH means that the solution has a lower basic character.
While solution with higher pH means that the solution has a higher basic character.
When we have a 0.1 M solution of a strong base or a weak base, the weak base will have a lower pH because it is not completely dissociated to produce OH⁻ ions.
While, strong base dissociates completely to produce OH⁻ ions, so it will has higher basic character and thus has a higher pH value.
So, weak base will have the lower pH value.
2) Which would have a higher pH, a 0.1 M solution of a strong acid, or a weak acid? Why?
For Acids:
Solution with lower pH means that the solution has a higher acidic character.
While solution with higher pH means that the solution has a lower acidic character.
When we have a 0.1 M solution of a strong acid or a weak acid, the weak acid will have a higher pH because it is not completely dissociated to produce H⁺ ions, so it has a lower acidic character.
While, strong acid dissociates completely to produce H⁺ ions, so it will has higher acidic character and thus has a lower pH value.
So, weak acid will have the higher pH value.
Calculate the molarity of 48.0 mL of 6.00 M H2SO4 diluted to 0.250 L .
Answer:
1.152 M.
Explanation:
It is known that the no. of millimoles of a substance before dilution is equal to the no. of millimoles after dilution.∴ (MV) before dilution = (MV) after dilution
before dilution: M = 6.0 M, V = 48.0 mL.
after dilution: M = ??? M, V = 0.25 L = 250.0 mL.
∴ M after dilution = (MV) before dilution/(V) after dilution = (6.0 M)(48.0 mL)/(250.0 mL) = 1.152 M.
To calculate the molarity of the diluted solution, use the formula M1V1 = M2V2 and plug in the values to find the final molarity.
Explanation:To calculate the molarity of the diluted solution, we can use the formula:
M1V1 = M2V2
Where M1 is the initial molarity, V1 is the initial volume, M2 is the final molarity, and V2 is the final volume.
Plugging in the values:
(6.00 M)(48.0 mL) = (M2)(0.250 L)
and solving for M2, we find:
M2 = (6.00 M)(48.0 mL) / (0.250 L) = 1152 M
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An atom of lithium-7 has an equal number of(1) electrons and neutrons(2) electrons and protons(3) positrons and neutrons(4) positrons and protons
Answer: Electrons and protons
An atom of lithium-7 has an equal number of electrons and protons. Therefore, the correct option is option 2.
What is lithium?Lithium is a chemical substance with the atomic number three as well as the symbol Li. The material is a delicate alkali metal in white-silver. Under normal conditions, it is both the lowest population metal and the least populated inorganic element. Because lithium is an extremely reactive as well as flammable alkali metal, it must be stored in a vacuum.
When cut, it has a glossy luster, but wet air quickly corrodes it, turning it into an olive drab silvery gray, eventually merely a black patina. Only compounds, particularly pegmatitic minerals, which has also historically been the primary source of lithium, may exist naturally. An atom of lithium-7 has an equal number of electrons and protons.
Therefore, the correct option is option 2.
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The balanced equation given below means: CH4 + 2 O2 → CO2 + 2H2O The balanced equation given below means: CH4 + 2 O2 → CO2 + 2H2O One molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water. One gram of methane reacts with two grams of oxygen to produce one gram of carbon dioxide and two grams of water. One mole of methane reacts with two moles of oxygen to produce one mole of carbon dioxide and 2 moles of water. One mole of methane reacts with two moles of oxygen to produce one mole of carbon dioxide and 2 moles of water, one gram of methane reacts with two grams of oxygen to produce one gram of carbon dioxide and two grams of water and one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water. One mole of methane reacts with two moles of oxygen to produce one mole of carbon dioxide and 2 moles of water and one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.
Answer:
See below.
Explanation:
CH4 + 2 O2 → CO2 + 2H2O
One molecule of methane reacts with 2 molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.
It is also true if we replace the word molecule by mole.
Answer : The correct option is,
One molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.
One mole of methane reacts with two moles of oxygen to produce one mole of carbon dioxide and 2 moles of water.
Explanation :
The given balanced chemical reaction is,
[tex]CH_4+2O_2\rightarrow CO_2+2H_2O[/tex]
Balanced chemical reaction : It is defined as the reaction in which the number of atoms of individual elements present on reactant side must be equal to the product side.
The given chemical reaction is a balanced reaction.
By the stoichiometry we can say that,
One molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.
or,
One mole of methane reacts with two moles of oxygen to produce one mole of carbon dioxide and 2 moles of water.
three diagnostic characteristics of an acid are:
three diagnostic characteristics of a base are:
Answer:
Explanation:
An acid:
According to Arrhenius Theory, is a substance that interacts with water to produce excess hydrogen ion in an aqeous solution. The Bronsted -Lowry Theory defines an acid as a proton donor. The Lewis Theory states that an acid is an electron pair acceptor.A base:
Arrhenius defined a base as a substance which interacts with water to yield excess hydroxide ions in an aqeous solution. Bronsted-Lowry defined a base as a proton acceptor. The Lewis Theory described a base as an electron pair donor.Acids and bases have unique diagnostic characteristics that can be used to identify them. Acids taste sour, turn blue litmus paper red, and react with metals to produce hydrogen gas. Bases taste bitter, turn red litmus paper blue, and feel slippery.
Explanation:Three diagnostic characteristics of an acid:
An acid tastes sour.An acid turns blue litmus paper red.An acid reacts with metals to produce hydrogen gas.Three diagnostic characteristics of a base:
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Pastoral farming is best described as _______. a. a method of raising livestock and moving herds b. an African method of agriculture c. a method of cultivating crops on poor soils d. a common method of desert farming Please select the best answer from the choices provided A B C D
Answer:
Pastoral farming is best described as a method of raising livestock and moving herds. (a.)
How does water vapor get into the atmosphere?
Answer:
through the water cycle
Explanation:
is HNO3 (aq) an acid or a base?
Answer:
HNO3 (aq) is an acid
Explanation:
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The stability of an isotope is based on its
Answer:
It is believed that the stability of an isotope is based on the ratio of neutrons to protons.
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What do electromagnetic waves carry? How are they produced Through which media can they move? Where do they transfer energy? What do they not transfer? What do mechanical waves carry? How are they produced? Through which media can they move? Where do they transfer energy? What do they not transfer?
Answer:
they are transfer from the towers
Explanation:
Given that Kw for water is 2.4× 10–14 at 37 °C, compute the pH of a neutral aqueous solution at 37 °C, which is the normal human body temperature.
Answer:
pH = 6.81.
Explanation:
The ionization of water is given by the equation :H₂O(l) ⇄ H⁺(aq) + OH⁻(aq),
The equilibrium constant (Kw) expression is:
Kw = [H⁺][OH⁻] = 2.4 x 10⁻¹⁴.
in pure water and neutral aqueous solution, [H⁺] = [OH⁻]
So, Kw = [H⁺]²
∴ 2.4 x 10⁻¹⁴ = [H⁺]²
∴ [H⁺] = 1.55 x 10⁻⁷ M.
∵ pH = - log [H⁺]
pH = - log (1.55 x 10⁻⁷) = 6.81.
What is the total reduction potential of a cell in which lithium (li) is reduced and mercury (hg) is oxidized?
Answer: The total reduction potential of the cell is -3.89 V.
Explanation:
We are given:
Reduction of lithium follows the reaction:[tex]Li^++e^-\rightarrow Li[/tex]
The standard reduction potential for this is -3.04 V
Oxidation of mercury follows the reaction:[tex]Hg\rightarrow Hg^{2+}+2e^-[/tex]
The standard reduction potential for this is -0.85 V
The cell formed by these half reactions is: [tex]Hg/Hg^{2+}||Li^+/Li[/tex]
The cell potential, [tex]E^o_{cell}=E^o_{oxidation}+E^o_{reduction}[/tex]
[tex]E^o_{cell}=[-0.85+(-3.04)]=-3.89V[/tex]
Hence, the total reduction potential of the cell is -3.89 V.
Which of the following is an incorrect pairing?
a. CH2::CHCH2CH2CH2CH2CH2CH3, alkene
b. CH3OCH3, amine
c. CH3CH2OH, alcohol
d. (CH3)2CO, ketone
Answer:
b. CH3OCH3, amine.
Explanation:
It is not an amine It is ethyl ether.
The option that is incorrect pairing is b. CH3OCH3, amine.
What are aminesCH3OCH3 represents the chemical formula for dimethyl ether, which is a type of ether. Ethers are organic compounds characterized by an oxygen atom linking two alkyl or aryl groups. They are not classified as amines.
Amines, on the other hand, are a different class of organic compounds that contain a nitrogen atom bonded to carbon atoms. They are typically named with the suffix "-amine" and can be primary, secondary, or tertiary depending on the number of alkyl or aryl groups bonded to the nitrogen atom.
Therefore, the pairing of CH3OCH3 with amine is incorrect, as CH3OCH3 is an ether, not an amine.
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Why is the melting of ice not a chemical change?
Answer:
Chemical change is basiclly chemical reaction that creates new substances, sometimes can be hard to observed. The melting of the ice only involves in changing the form of the matter, from solid to liquid form, it doesn't transform the substance which is water into another substance. Therefore, the melting of ice is not a chemical change, but rather a physical one.
Answer:
A new substance is not formed
Explanation:
Its still water just not physically
When you perform this reaction, what substances could remain at the end of the reaction? Check all that apply.
excess reactant aqueous copper chloride
excess reactant aluminum
oxygen
product solid copper
carbon dioxide
product aqueous aluminum chloride
water
Answer:
a.) excess reactant aqueous copper chloride.
b.) excess reactant aluminum.
d.) product solid copper.
f.) product aqueous aluminum chloride.
g.) water.
Explanation:
just did the lab, here's the answers :)
Excess reactant aluminum, oxygen, product solid copper, product aqueous aluminum chloride, water could remain at the end of the reaction.
Explanation:
When performing the reaction between aluminum and copper chloride, there are several substances that could remain at the end of the reaction:
Excess reactant aluminum: If aluminum is present in excess, then it would remain at the end of the reaction.
Oxygen: If oxygen is introduced into the reaction, it could remain as a result of incomplete combustion.
Product solid copper: Copper is formed as a product of the reaction between aluminum and copper chloride.
Product aqueous aluminum chloride: Aluminum chloride is also formed as a product of the reaction.
Water: Water can also be present as a product depending on the conditions of the reaction.
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Which aqueous solution has the highest boiling point at standard pressure?(1) 1.0 M KC1(aq) (3) 2.0 M KCl(aq)(2) 1.0 M CaC12(aq) (4) 2.0 M CaC12(aq)
Answer:
(4) 2.0 M CaCl₂(aq).
Explanation:
Adding solute to water elevates the boiling point.The elevation in boiling point (ΔTb) can be calculated using the relation:ΔTb = i.Kb.m,
where, ΔTb is the elevation in boiling point.
i is the van 't Hoff factor.
van 't Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved and the concentration of a substance as calculated from its mass. For most non-electrolytes dissolved in water, the van 't Hoff factor is essentially 1.Kb is the molal elevation constant of water.
m is the molality of the solution.
(1) 1.0 M KCl(aq):
i for KCl = no. of particles produced when the substance is dissolved/no. of original particle = 2/1 = 2.
suppose molarity = molality, m = 1.0 m,
∴ ΔTb for (1.0 M KCl) = i.Kb.m = (2)(Kb)(1.0 m) = 2(Kb).
(2) 2.0 M KCl(aq):
i for KCl = no. of particles produced when the substance is dissolved/no. of original particle = 2/1 = 2.
suppose molarity = molality, m = 2.0 m,
∴ ΔTb for (1.0 M KCl) = i.Kb.m = (2)(Kb)(2.0 m) = 4(Kb).
(3) 1.0 M CaCl₂(aq):
i for CaCl₂ = no. of particles produced when the substance is dissolved/no. of original particle = 3/1 = 3.
suppose molarity = molality, m = 1.0 m,
∴ ΔTb for (1.0 M KCl) = i.Kb.m = (3)(Kb)(1.0 m) = 3(Kb).
(4) 2.0 M CaCl₂(aq):
i for CaCl₂ = no. of particles produced when the substance is dissolved/no. of original particle = 3/1 = 3.
suppose molarity = molality, m = 2.0 m,
∴ ΔTb for (1.0 M KCl) = i.Kb.m = (3)(Kb)(2.0 m) = 6(Kb).
So, the aqueous solution has the highest boiling point at standard pressure is: (4) 2.0 M CaCl₂(aq).
The aqueous solution with the highest boiling point at standard pressure is the 2.0 M CaCl2 solution because it has the highest concentration and dissociates into the most ions.
Explanation:The boiling point of an aqueous solution is influenced by the concentration of solutes due to the colligative property known as boiling point elevation. According to the principle of boiling point elevation, each mole of solute particles will raise the boiling point of 1 liter of water by 0.51°C. Taking this into account, the boiling point of a solution is also affected by the number of particles into which each formula unit dissociates in solution. For example, CaCl2 dissociates into three ions (one calcium ion and two chloride ions).
Given the options, the aqueous solution with the highest boiling point at standard pressure is the 2.0 M CaCl2 solution (Option 4). This is because it has the highest concentration of particles in solution: for every mole of CaCl2 there are three moles of ions due to dissociation, and its molarity is the highest among the given solutions.
A mixture of iron and sulfur can be separated by
distillation, magnetic attraction, filtration
How many grams of NaNO3 would have to be added to 100. grams of water at 45°C to make a saturated solution of this salt? 1. 100. 2. 110. 3. 120. 4. 130.
Answer:
2. 110.
Explanation:
Kindly find the attached image.From the solubility curve, you can find that at 45°C to make a saturated solution of this salt, you should add 110 g of NaNO₃.
So, the right choice: 2. 110.The dissolution of the solute in the solvent at the specified temperature is termed as solubility. The maximum solubility of sodium nitrate in the water at 45 degree Celsius in 110 grams.
What is the solubility curve?The increase in temperature of the solvent resulted in the weaker the intermolecular force of solvent, and increases the solubility.
The solubility curve is drawn for the maximum amount of solute that can be dissolved in the solvent at the specified temperature.
From the solubility curve of sodium nitrate, the maximum amount of sodium nitrate in the water at 45 degree Celsius is 110 grams. Thus, option 2 is correct.
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Interpolate: Use the equation to determine what the student enrollment in 2003 likely was.
students
Answer:
1244 students
Explanation:
That would be y = 82*3 + 998
= 1244.
Answer:
The expected student enrollment in 2003 is 1244.
Explanation:
The given diagram it is clear that the graph represents the relationship x and y, where x is number of years since 2000 and y is number of student enrollment.
From the given figure it is clear that the equation of best fit line is
[tex]y=82x+998[/tex] .... (1)
We need to find the expected student enrollment in 2003.
Year 2003 is 3 years since 2000.
Substitute x=3 in equation (1) to find the expected student enrollment in 2003.
[tex]y=82(3)+998[/tex]
[tex]y=246+998[/tex]
[tex]y=1244[/tex]
Therefore the expected student enrollment in 2003 is 1244.
How many valence electrons are in atom of radon?
Answer: 8
Explanation: Radon has 8 valence electrons. Radon is considered stable with a complete octet of electrons, filling the s and p orbitals.
An acidified solution was electrolyzed using copper electrodes. A constant current of 1.18 A caused the anode to lose 0.584 g after 1.52 ✕ 103 s. (a) What is the gas produced at the cathode and what is its volume at STP? name of gas volume of gas WebAssign will check your answer for the correct number of significant figures. L (b) Given that the charge of an electron is 1.6022 ✕ 10−19 C, calculate Avogadro's number. Assume that copper is oxidized to Cu2+ ions.
Answer:
[tex]\boxed{\text{(a) 209 mL; (b) } 6.09 \times 10^{23}}[/tex]
Explanation:
(a) Gas produced at cathode.
(i). Identity
The only species known to be present are Cu, H⁺, and H₂O.
Only the H⁺ and H₂O can be reduced.
The corresponding reduction half reactions are:
(1) 2H₂O + 2e⁻ ⇌ H₂ + 2OH⁻; E° = -0.8277 V
(2) 2H⁺ +2e⁻ ⇌ H₂; E° = 0.0000 V
Two important points to remember when using a table of standard reduction potentials:
The higher up a species is on the right-hand side, the more readily it will lose electrons (be oxidized). The lower down a species is on the left-hand side, the more readily it will accept electrons (be reduced}.H⁺ is below H₂O, so H⁺ is reduced to H₂.
The cathode reaction is 2H⁺ +2e⁻ ⇌ H₂, and the gas produced at the cathode is hydrogen.
(ii) Volume
a. Anode reaction
The only species that can be oxidized are Cu and H₂O.
The corresponding half reactions are:
(3) Cu²⁺ + 2e⁻ ⇌ Cu; E° = 0.3419 V
(4) O₂ + 4H⁺ + 4e⁻ ⇌ 2H₂O E° = 1.229 V
Cu is above H₂O, so Cu is more easily oxidized.
The anode reaction is Cu ⇌ Cu²⁺ + 2e⁻.
b. Overall reaction:
Cu ⇌ Cu²⁺ + 2e⁻
2H⁺ +2e⁻ ⇌ H₂
Cu + 2H⁺ ⇌ Cu²⁺ + H₂
c. Moles of Cu lost
[tex]n_{\text{Cu}} = \text{0.584 g } \times \dfrac{\text{1 mol}}{\text{63.55 g}} = 9.190 \times 10^{-3}\text{ mol Cu}[/tex]
d. Moles of H₂ formed
[tex]n_{\text{H}_{2}}} = 9.190 \times 10^{-3}\text{ mol Cu} \times \dfrac{\text{1 mol H}_{2}}{\text{1 mol Cu}} =9.190 \times 10^{-3}\text{ mol H}_{2}[/tex]
e. Volume of H₂ formed
Volume of 1 mol at STP (0 °C and 1 bar) = 22.71 mL
[tex]V = 9.190 \times 10^{-3}\text{ mol}\times \dfrac{\text{22.71 L}}{\text{1 mol}} = \text{0.209 L} = \boxed{\textbf{209 mL}}[/tex]
(b) Avogadro's number
(i) Moles of electrons transferred
[tex]\text{Moles of electrons} = 9.190 \times 10^{-3}\text{ mol Cu}\times \dfrac{\text{2 mol electrons}}{\text{1 mol Cu}}\\\\\\= \text{0.018 38 mol electrons}[/tex]
(ii) Number of coulombs
Q = It
Q = \text{1.18 C/s} \times 1.52 \times 10^{3} \text{ s} = 1794 C
(iii). Number of electrons
[tex]n = \text{ 1794 C} \times \dfrac{\text{1 electron}}{1.6022 \times 10^{-19} \text{ C}} = 1.119 \times 10^{22} \text{ electrons}[/tex]
(iv) Avogadro's number
[tex]N_{\text{A}} = \dfrac{1.119 \times 10^{22} \text{ electrons}}{\text{0.018 38 mol}} = \boxed{6.09 \times 10^{23} \textbf{ electrons/mol}}[/tex]