Is rain turning to snow a physical or chemical change?
After 252 days, a 12.0-g sample of the radioisotope scandium-46 contains only 1.5 g of the isotope. what is the half-life of scandium-46
The half-life of scandium-46 is determined by noting that after 252 days, the mass of the isotope reduces from 12.0 g to 1.5 g, which is 1/8 of the original mass, indicating that three half-lives have passed. Dividing the total time by 3 gives us a half-life of 84 days for scandium-46.
To determine the half-life of scandium-46, we use the fact that after a certain number of half-lives, the remaining mass of a radioactive substance is half of its initial mass after each half-life period. In the given problem, a 12.0-g sample of scandium-46 decays to 1.5 g after 252 days. This decay represents a reduction to 1/8 of the original mass, indicating that three half-lives have passed (since 12.0 / 2 / 2 / 2 = 1.5).
Initial mass of scandium-46: 12.0 gFinal mass of scandium-46 after 252 days: 1.5 gMass reduction to 1/8 indicates 3 half-lives.Since 3 half-lives are equivalent to 252 days, we can find the length of a single half-life by dividing the total time by 3:
252 days ÷ 3 = 84 days
Therefore, the half-life of scandium-46 is 84 days.
When comparing the activation energy between different exothermic reactions, as the activation energy decreases at a given temperature, the reaction rate increases because the _______?
Answer:
number of successful effective collisions is higher
How is data not actually obtained from the experiment represented in a line graph?
with a double line
with only dots
with a colored line
with a broken line
Answer: Broken line
Explanation:
When you collect data in an experiment, you usually need a model where you can analyze the data.
One way of doing this is when in an experiment you expect a given behavior determined by a function (or data obtained by previous investigations), you can graph your obtained data over the graph of the function (or previous data), and in this way, you can see if your data fits in the model.
You usually will graph your obtained data with dots, so usually, we graph the other things with a broken line. This is because if you use a colored line and you do some kind of fitting with your data, the lines may "clash" into each other, making the graph hard to read.
Ionization energy and electron affinity both express the general attraction of an atom for
Ionization energy is the energy required to remove an electron from an atom. Meanwhile, Electron affinity is the energy required to add an electron to an atom. So we can see that the two are opposite variables. However, they both refers to general attraction of an atom for “electron”.
What particles in an atom can increase or decrease without changing the identity of the element?
In the preparatory reaction which involves moving pyruvic acid into the mitochondrion
Which one of the following chemical formulas represents an organic molecule
What state must a substance be in order to analyze it using uv vis spectroscopy?
For the angular momentum quantum number l=2 , how many possible values are there for the magnetic quantum number (m subscript l)?
1
3
5
8
The angular momentum quantum number l = 2 corresponds to 5 possible values for the magnetic quantum number m, which are -2, -1, 0, 1, and 2.
For the angular momentum quantum number,
l = 2, the number of possible values for the magnetic quantum number (m) is given by the formula 2l + 1. Plugging in
l = 2, we get 2(2) + 1 = 5 possible values.
Therefore, the values of m that are possible for
l = 2 are -2, -1, 0, 1, and 2, which confirms that there are 5 possible values for the magnetic quantum number when l is 2.
Heat is so closely related to _____, the same units are used to measure both.
Answer:
I am pretty sure temperature is wrong. It is actually work.
Explanation:
Scientists use the term joule(s) for heat. Temperature is measured in celcius, kelvin, fahrenheit. Work also uses the same term for measuring; joules. I am pretty sure the right answer is actually work, even though temperature sounds more correct. I learned this in science so I think I am right.
write out the electron configurations for (a) potassium and (b) cobalt. how many unpaired electrons does each possess?
When a sample of atoms is heated and releases light of certain wavelengths, it is called what?
The answer is emission spectrum. It is the range of frequencies of electromagnetic radiation produced because of an atom or molecule generating a transition from a high energy state to a lower energy state. The photon energy of the produced photon is equivalent to the energy change between the two states. There are many conceivable electron changes for each atom, and each change has a precise energy difference.
What natural method of separating mixtures happens in reservoirs over a long period of time?
Use common factors to write 2 fractions equivalent to 6/42.
A) 4/16,2/21
B) 2/14,3/21
C) 2/14,4/16
D) 7/25,3/21
Answer:
The correct answer is option B.
Explanation:
[tex]\frac{6}{42}=\frac{1}{7}[/tex]
A) [tex]\frac{4}{16}=\frac{1}{4}\neq \frac{1}{7}[/tex]
[tex]\frac{2}{21}=\frac{2}{21}\neq \frac{1}{7}[/tex]
Both fraction are not equivalent to [tex]\frac{1}{7}[/tex].
B)[tex]\frac{2}{14}=\frac{1}{7}= \frac{1}{7}[/tex]
[tex]\frac{3}{21}=\frac{1}{7}= \frac{1}{7}[/tex]
Both fraction are equivalent to [tex]\frac{1}{7}[/tex].
C) [tex]\frac{2}{14}=\frac{1}{7}= \frac{1}{7}[/tex]
[tex]\frac{4}{16}=\frac{1}{4}\neq \frac{1}{7}[/tex]
Both fraction are not equivalent to [tex]\frac{1}{7}[/tex].
D)[tex]\frac{7}{25}=\frac{7}{25}\neq \frac{1}{7}[/tex]
[tex]\frac{3}{21}=\frac{1}{7}= \frac{1}{7}[/tex]
Both fraction are not equivalent to [tex]\frac{1}{7}[/tex].
how many moles of copper must react to form 0.854 mol ag
How many moles of copper must react to form 0.854 mol Ag? =0.427
Identify what a bomb calorimeter measures. identify what a bomb calorimeter measures. measures δh for reduction solutions measures δe for combustion reactions measures δh for aqueous solutions measures δt for aqueous solutions measures δe for oxidation reactions
A bomb calorimeter is a device which is used to determine the change in enthalpy by measuring the change in temperature given the mass and heat capacity of the overall system by using the formula:
δh = m C (T2 – T1)
This is done by combusting the material in oxygen.
Hence the answer is:
measures δe for combustion reactions
A bomb calorimeter measures ΔE for combustion reactions. So correct option is B.
B) measures ΔE for combustion reactions.
A bomb calorimeter is a device used to measure the heat released or absorbed during a combustion reaction. It is a sealed container that is filled with oxygen and the reactants. The reaction is ignited, and the heat released is measured by the rise in temperature of the water surrounding the bomb.
The heat released in a combustion reaction is equal to the change in energy (ΔE) of the reaction. This is because the energy released is used to break the bonds in the reactants and form the bonds in the products. The heat released can be used to calculate the enthalpy change (ΔH) of the reaction, but only if the reaction is carried out at constant pressure.
Bomb calorimeters are used to measure the energy content of fuels, such as gasoline and coal. They are also used to measure the energy content of food.
The other options you have listed are incorrect. A bomb calorimeter does not measure ΔH for oxidation solutions, ΔH for hydrolysis solutions, ΔT for hydrolysis solutions, or ΔE for aqueous reactions.
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The complete question is:
Identify what a bomb calorimeter measures.
A) measures ΔH for reduction solutions
B) measures ΔE for combustion reactions
C) measures ΔH for aqueous solutions
D) measures ΔT for aqueous solutions
E) measures ΔE for oxidation reactions
How does dalton's atomic theory support the law of conservation of mass?
Final answer:
Dalton's atomic theory supports the law of conservation of mass by positing that atoms, the indivisible units of matter, are neither created nor destroyed during chemical reactions, ensuring mass remains constant in a closed system.
Explanation:
How does Dalton's atomic theory support the law of conservation of mass? John Dalton's atomic theory re-introduced the idea of atomism, which suggests that all matter is composed of small, indestructible units known as atoms. This theory aligns closely with the law of conservation of mass, established by Antoine Lavoisier, which states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations.
Dalton proposed that chemical reactions involve the rearrangement of atoms that are combined, separated, or rearranged, but never created or destroyed. Therefore, the total mass of reactants in a chemical reaction equals the total mass of the products. This agreement with the law of conservation of mass is a fundamental principle showing that during any chemical process in a closed system, the mass remains constant. Dalton's theory provides a microscopic explanation of this macroscopic observation, illustrating that the mass conservation is due to the conservation of atoms in chemical processes.
If an element like copper consists of only one kind of atom, it means it cannot be broken down into simpler substances. This implies that atoms, the fundamental building blocks of matter, are neither created nor destroyed during a chemical change, reinforcing the concept of mass conservation. This understanding marks a pivotal development in the field of chemistry, allowing for the quantitative study of chemical reactions and the advancement of chemical science.
A 25-ml sample of river water was titrated with 0.0010 m k2cr2o7 and required 8.3 ml to reach the end point. what is the chemical oxygen demand, in milligrams of o2 per liter, of the sample?
First let us calculate the moles of K2Cr2O7 that was supplied.
moles K2Cr2O7 = 0.0010 M * 0.0083 L = 8.3x10^-6 mol
From the chemical formula itself, we see that there are 7 O for every mole of K2Cr2O7 or 3.5 O2. Therefore:
moles O2 = 8.3x10^-6 mol K2Cr2O7 * (3.5 mol O2 / 1 mol K2Cr2O7)
moles O2 = 2.905x10^-5 mol O2
Calculating for the mass of O2 in mg:
mass O2 = 2.905x10^-5 mol O2 * (32 g / mol) * (1000 mg / g)
mass O2 = 0.9296 mg
Therefore the chemical oxygen demand (COD) is:
COD = 0.9296 mg / (0.025 L)
COD = 37.184 mg/L
The Chemical Oxygen Demand (COD) for the given sample is calculated based on the amount of K2Cr2O7 used in the analysis. Considering this calculation, the COD of the analyzed sample comes around 63,744 mg/L or approximately 63.744 g/L.
Explanation:The Chemical Oxygen Demand (COD) can be determined using the titrated volume of potassium dichromate (K2Cr2O7) required to reach the endpoint of the titration. In this case, the dichromate ion (Cr2O7) is reduced by any present organic matter in the water sample, while being oxidized to Cr, and each Cr2O7 ion utilizes 6 moles of oxygen in the process.
In this scenario, the volume of K2Cr2O7 used is 8.3 ml with a molarity of 0.0010 M. Hence, the total moles of oxygen used can be calculated as 8.3 ml x 0.0010 moles/ml x 6 moles O2/ mole Cr2O7 = 0.0498 moles O2.
As the question requires the answer in milligrams per liter (mg/L), we have to convert moles of O2 to mg and the sample volume to L. This gives us 0.0498 moles x 32 g/mole x1000 mg/g = 1593.6 mg O2 in the original 0.025 L sample. Thus, the Chemical Oxygen Demand (COD) of the sample is 1593.6 mg /0.025 L = 63,744 mg/L or approximately 63.744 g/L.
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How many grams of calcium must be combined with phosphorus to form one mole of the compound Ca3P2?
Final answer:
To form one mole of Ca3P2, 120.234 grams of calcium are required based on the atomic mass of calcium and the stoichiometry of the compound.
Explanation:
To determine how many grams of calcium must be combined with phosphorus to form one mole of the compound Ca3P2, we need to first understand that Ca3P2 consists of 3 calcium (Ca) atoms and 2 phosphorus (P) atoms. The atomic mass of calcium is 40.078 amu (atomic mass units), and that of phosphorus is 30.973761 amu.
The total mass of calcium in Ca3P2 can be calculated as follows:
(3 atoms) × (40.078 amu/atom) = 120.234 amuTo convert this atomic mass to grams, we use the molar mass concept where 1 mole of any substance equals its atomic or molecular mass in grams. Therefore, we need:
120.234 grams of calciumTo form one mole of Ca3P2, no information on the amount of phosphorus is needed since the question only asks for the amount of calcium required.
Is electron affinity the opposite of ionization energy?
Would a calcium ion (ca2+) and a chloride ion attract or repel each other?
Final answer:
A calcium ion (Ca²+) and a chloride ion (Cl-) attract each other due to their opposite charges, forming an ionic bond in the compound calcium chloride (CaCl²).
Explanation:
A calcium ion (Ca²+) and a chloride ion (Cl−) will attract each other due to the opposite charges they carry. Calcium donates two electrons to achieve a stable electron configuration, becoming a Ca²+ ion. Each electron is then accepted by a chlorine atom, which becomes a Cl− ion. This transfer leads to the formation of the ionic compound calcium chloride (CaCl²), where the attraction between the positively charged calcium ions and the negatively charged chloride ions results in a strong electrostatic force that holds the compound together in a lattice structure. The ionic bonding between Ca²+ and Cl− is a result of the coulombic attraction described by Coulomb's law, which states that opposite charges attract each other.
plants that can live in water soaked soil are able to survive in the what ecosystem?
A glass of cold milk sometimes forms a coat of water on the outside of the glass (often referred to as ‘sweat'). how does most of the water get there?
Use the given figure to complete the statement below.
∠1 and ∠2 are angles. ANSWERS -Obtuse complementary adjacent vertical
adjacent is the correct answer
The angles ∠1 and ∠2 are adjacent to each other.
What is a Supplementary Angle ?When the total of two angles equals 180 degrees, they are referred to as supplementary angles because they form a linear angle when combined. When the sum of two angles equals 90 degrees, they are considered to be complimentary angles, and they produce a right angle when they are combined.
In the given figure ∠1 and ∠2 are supplementary angle and adjacent to each other
Therefore in the options given ∠1 and ∠2 are adjacent to each other.
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What are the final or new substances (molecule) in a chemical equation called?
When an oxygen atom is attached to a carbon atom the carbon atom becomes more?
Answer: Reduced
Explanation: When an oxygen atom is attached to a carbon atom, the carbon atom becomes reduced.
pure substance definition in chemistry?
A pure substance in chemistry is a material with a constant composition and unique set of properties, classified as either an element or a compound. Elements contain only one type of atom, while compounds consist of chemically bonded atoms of different types. Pure substances can be identified by their distinct physical properties and purity tests like chromatography.
Explanation:In chemistry, a pure substance refers to materials that have a constant composition and a unique set of properties across the entire sample. Pure substances are classified into two categories: elements and compounds. An element is a pure substance that consists of a single type of atom and cannot be chemically broken down into simpler substances. Gold, oxygen, and copper are well-known examples of elements. On the other hand, compounds are pure substances that consist of two or more atoms chemically bonded together, such as water (H2O) which is made from hydrogen and oxygen. Unlike mixtures, compounds have fixed proportions of atoms and can only be separated into their constituent elements by chemical reactions.
Pure substances have distinct and consistent physical properties like melting and boiling points. In contrast, mixtures have variable compositions and may exhibit a range of melting and boiling points. Testing for purity can involve methods like chromatography, where a pure substance yields a single component, while impure substances produce multiple components.
Why is the second ionization energy greater than the first ionization energy? (1 Point)
A. It is more difficult to remove a second electron from an atom
B. The size of atoms increases down a group
C. The size of anions decreases across the period
D. The nuclear attraction from protons in the nucleus decreases
In case of the first ionization energy, the first electron is removed from a neutral atom; while in the second ionization energy the electron is removed from a positively charged ion which is found to be an electron deficient species.
Also when the second electron was removed the effective nuclear charge increases as compared to the first electron removal.
As a result there is a strong attraction between the nucleus and the outermost electron of the element. Therefore, the second ionization energy is observed to be higher than the first ionization energy of an element.
Use the given figure to complete the statement below.
∠2 and ∠4 are angles. supplementary adjacent vertical complementary
Easy, its vertical :3
Answer: ∠2 and ∠4 are vertical angles.
Explanation: We are given two linear lines that intersect each other and forms angles.
Theorem: When two lines intersect, the vertical angle are congruent to each other which means that the two angles are equal. Vertical angles are the angles that are opposite to each other.
In the given figure, ∠2 and ∠4 are opposite to each other, hence they are considered as vertical angles.
∠2 = ∠4 (From above theorem)