Answer:
The rate at which the solute dissolves will increase.
Explanation:
If a solution is stirred, the rate at which a solute dissolves would increase substantially provided the solution is not yet saturated.
Stiring would cause more of the solution to come in contact with every part of the solute. It will increase the surface area of contact for the solution to act which will shoot up the rate of reaction. Stiring helps to bring solutes in solutions into a more close contact with the molecules or compounds of the medium.
Which type of bonding involves the complete transfer of a valence electron from a less electronegative atom to a more electronegative one?
Answer:
Ionic or electrovalent bonds
Explanation:
Ionic or electrovalent bonds are interatomic or intramolecular bonds which are formed between two kinds of atoms having a large electronegativity difference usually 2.1.
Electronegativity is the property that combines the ability of an atom to gain or lose electrons. It is expressed as the tendency with which atoms of elements attracts valence electrons in a chemical bond.
In this bond type, a metal transfers its electrons to a more electronegative atom which is a non-metal.
The answer is: a. ionic bonding.
Ionic bond is the electrostatic attraction between oppositely charged ions (cations and anions).
(brainliest would be great)
For example, compound magnesium chloride (MgCl₂) has ionic bond.
In this example, chlorine is large company, because it has greater electronegativity than magnesium (small company) and take electrons (assets) from it.
Magnesium (Mg) transfers two electrons, became positive cation, to chlorine (Cl), which became negative anion.
Magnesium is metal from group 2 and chlorine is nonmetal from group 17 of the Periodic table.
Electronegativity (χ) is a property that describes the tendency of an atom to attract a shared pair of electrons.
f 1.5 mol of NaBH4 react, how many moles of B2H6 are formed? 2 NaBH4(aq) + H2SO4(aq) → 2 H2(g) + Na2SO4(aq) + B2H6(g)
Answer:
[tex]\boxed{ \text{0.75 mol}}[/tex]
Explanation:
(a) Balanced equation
2NaBH₄ + H₂SO₄ ⟶ 2H₂ + Na₂SO₄ + B₂H₆
(b) Calculation
You want to convert moles of NaBH₄ to moles of B₂H₆
The molar ratio is 1 mol B₂H₆:2 mol NaBH₄
[tex]\text{Moles of B$_{2}$H$_{6}$} =\text{1.5 mol NaBH$_{4}$} \times \dfrac{\text{1 mol B$_{2}$H$_{6}$}}{\text{2 mol NaBH$_{4}$}} = \textbf{0.75 mol B$_{2}$H$_{6}$}\\\\\text{The reaction will produce }\boxed{ \textbf{0.75 mol of B$_{2}$H$_{6}$}}[/tex]
Now starting with lithium, look at its electron configuration. Then look at all eight elements in the second period from lithium to neon (Ne). What do you notice about the change in the electron configuration as you go from left to right
Answer:
Explanation:
Lithium is the first element in the second period. The second period has a total number of eight elements in all. The number of electrons in a lithium atom is 3.
The electronic configuration of lithium is 1s²2s¹. Lithium has just a single electron in its outermost shell.
Moving from left to right across the second period, the number of electrons in the outermost shell of the elements increases till it reaches the octet i.e 8:
Be (4) : 1s²2s²
B (5): 1s²2s²2p¹
C (6): 1s²2s²2p²
N (7): 1s²2s²2p³
O(8): 1s²2s²2p⁴
F (9): 1s²2s²2p⁵
Ne(10): 1s²2s²2p⁶
As you go from left to right, the number of valence electrons increases by 1.
From left to right, the number of shell remains fairly constant. Li and Be has one electronic shell each while the rest of the elements in the period have two shells.
As we move from lithium to neon in the periodic table, the elements gain one electron each. Hence, their electron configuration increases sequentially, in line with their increasing atomic number.
Explanation:When starting with lithium and proceeding to neon across the second period of the periodic table, the atomic number increases from 3 to 10. The atomic number corresponds to the number of protons, which also equals the number of electrons in an atom for a neutral element. Accordingly, as we move from left to right, one observes an increase in the electron configuration, with each subsequent element gaining an additional electron. For instance, the electron configuration of lithium is 1s2 2s1, that of beryllium (the next element) is 1s2 2s2, and so on, till we reach neon with a configuration of 1s2 2s2 2p6. Hence, the number of electrons (and hence electron configuration) increases as we move from lithium to neon.
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why do cells appear different in distilled water than they do in 10% salt water?
Answee
the plant cells are placed in the salt solution, there is a higher concentration of water molecules in the cell and a lower concentration of water in the salt solution and thus a concentration gradient has been set up. the cell membrane is now pressed up against the cell wall and the cell is said to be turgid.
Answer:
i don't know
Explanation:
7.26 of a hydrate, Cu(NO3)2.xH2O, formed 2.4 g copper(II) oxide.
1) What is the number of moles of CuO formed?
2) What is the number of moles of Cu(NO3)2.xH2O in 7.26 g?
3) What is the mass of 1 mole of Cu(NO3)2.xH2O?
4) Mass of 1 mole of Cu(NO3)2 is 188g
5) What is the value of x in this hydrate?
Number of moles= mass/ molar mass
Or n=m/MM
n = number of moles
m = mass
MM = molar mass
1) n CuO = 2.4g / 79.54g/mol = 0.03 mol CuO
2) n Cu(NO3)2.xH2O = 7.26 g / 205.6 = 0.035 moles of Cu(NO3)2.xH2O
3) 205.6 g
Cu = 63.5 g
N = 14g
O =16g
H= 1 g
63.5+ (14+(16*3))*2+1*2+16 =205.6 g
4) yes is 188g
5) I don’t know, I assume was 1
1) The number of moles of CuO formed is 0.117 moles. 2) The number of moles of Cu(NO3)2.xH2O in the hydrate is 0.117 moles. 3) The mass of 1 mole of Cu(NO3)2.xH2O is 62 g. 4) The mass of 1 mole of Cu(NO3)2 is 188 g. 5) The value of x in the hydrate is -126 g/mol.
Explanation:In order to answer the given questions, we need to first find the molar mass of Cu(NO3)2.xH2O. The molar mass of Cu(NO3)2 is 187.55 g/mol. To find x, we can subtract the molar mass of Cu(NO3)2 from the molar mass of Cu(NO3)2.xH2O. The molar mass of Cu(NO3)2.xH2O is 249.55 - 187.55 = 62 g/mol. Now we can answer the questions:
The number of moles of CuO formed is equal to the number of moles of Cu(NO3)2.xH2O in the hydrate. Therefore, it is 7.26 g / 62 g/mol = 0.117 moles.Given that the mass of Cu(NO3)2.xH2O is 7.26 g, we divide it by the molar mass of Cu(NO3)2.xH2O to find the number of moles. Therefore, the number of moles of Cu(NO3)2.xH2O is 7.26 g / 62 g/mol = 0.117 moles.The molar mass of Cu(NO3)2.xH2O is 62 g/mol. Therefore, the mass of 1 mole of Cu(NO3)2.xH2O is 62 g.The mass of 1 mole of Cu(NO3)2 is given as 188 g.The value of x can be found by subtracting the molar mass of Cu(NO3)2 from the molar mass of Cu(NO3)2.xH2O. Therefore, x = 62 g/mol - 188 g/mol = -126 g/mol.Learn more about Calculating moles and molar mass here:https://brainly.com/question/34679795
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How is it possible for two neutral objects to become charged by rubbing them together? A. The binding force of the objects’ atoms overcomes the frictional force and their atoms become more tightly bound. B. The frictional force overcomes the atoms’ binding force, which releases an electron from the innermost orbit of one of the objects. C. There is no change in the objects. D. The frictional force overcomes the force that binds the electrons to the atoms, enabling the electrons to move elsewhere
Answer:
D. The frictional force overcomes the force that binds the electrons to the atoms, enabling the electrons to move elsewhere
Explanation:
Neutral objects becomes charged by rubbing them together due to the frictional force which overcomes the attractive force holding electrons together in an atom.
Friction is the resistance to flow or movement. When we rub bodies together, the movement of electrons becomes inhibited and this can cause an orbital electron loosely held in an atom to be pulled off as the force of friction increases. This mechanism would result in a body losing electron and another readily gaining that electron as they interact. The loss and gain of electrons causes a neutral body to become charged.
Answer:
its D
Explanation:
The molecular weight of carbon dioxide, CO2, is 44.00 amu, and the molecular weight of nitrous dioxide, NO2, is 46.01
amu, so NO2 diffuses
CO2
Answer:
Grahm's law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of the mass of its particles.
Molecular weight of NO2 = 46 g mol¹-
Molecular weight of CO2 = 44g mol¹-
Thus the compound which has a lower molecular mass will diffuse at a faster rate than the heavier compound. In this case, the molecular mass of NO2 is more than the CO2 so, NO2 will diffuse at a slower rate than the CO2 molecule.
Complete the table for ion charge based upon their losing or gaining electrons in the outer shell. (Use the periodic table as necessary.) Group Most Likely Ionic Charge # of Valence Electrons I +1 II +2 III +3 IV +4 or -4 V -3 VI -2 VII -1 VIII 0
Answer:
Explanation:
Group Most Likely Ionic Charge Number of Valence Electrons
I +1 1
II +2 2
III +3 3
IV +4 or -4 4
V -3 5
VI -2 6
VII -1 7
VIII 0 8
For elements in group IV and above, their ionic charge is (8-number of their valence electrons.)
Explanation:
Valence electrons are defined as the electrons which are present in the outermost shell of an atom.
The number of valence electrons in a particular group will be equal to the group number.
Number of valence electrons = Group number
The given table follows:
Group Most likely ionic charge No. of valence electrons
I +1 1
II +2 2
III +3 3
IV +4 or -4 4
V -3 5
VI -2 6
VII -1 7
VIII 0 8
What is the molarity of a solution that contains 289 grams of sugar in a 2 L solution? (Molar mass of sucrose is 342.2965g/mol). Show your work
Please answer ASAP!!
Answer:
0.422 mol/L.
Explanation:
Molarity (M) is the no. of moles of solute dissolved in a 1.0 L of the solution.M = (no. of moles of glucose)/(volume of the solution (L))
M = (mass/molar mass)of glucose / (volume of the solution (L)).
∴ M = (mass/molar mass)of glucose / (volume of the solution (L)) = (289 g/342.2965 g/mol)/(2.0 L) = 0.422 mol/L.
How does the oxidation state of Na change in the following reaction?
Li(s) + NaOH(aq) → LiOH(aq) + Na(s)
The oxidation state of Na decreases from 1 to 0 in this reaction Li (s) + NaOH (aq) → LiOH(aq) + Na(s).
What is Oxidation state ?Oxidation state is also called Oxidation number is defined as the number assigned to atoms in molecules to represent the general distribution of electrons.
What is a Chemical Reaction ?A chemical reaction is a process in which chemical bonds between atoms to break and reorganize, to form other new substances.
The given chemical reaction is
Li (s) + NaOH (aq) → LiOH(aq) + Na(s)
The oxidation state of Li is zero in the reactant side. The oxidation state of Na in the reactant side is 1. The oxidation state of Li in the product side is 1. The oxidation state of Na in reactant side is 0.
So the oxidation number of Na decreases from 1 to 0.
Thus from the above conclusion we can ay that The oxidation state of Na decreases from 1 to 0 in this reaction Li (s) + NaOH (aq) → LiOH(aq) + Na(s).
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Which statement explains why the bonds between non metals tend to be covalent?
The bonds are found to be nondirectional
They have large differences in electronegativity
They have small differences in electronegativity
They have ions that produce an electrostatic pull
They have small differences in electronegativity
i think thats right
Answer:
C.) They have small differences in electronegativity
one or more substances changing into one or more substances is an example of a
Hello There!
This is called a "Chemical Change"
A chemical change is when the composition of a substance changes. There are many signs of chemical changes. When a chemical change occurs, you can see a change in color. When a new color is visible that means that a new substance has been created. There also is a new smell "odor" this hints that a new substance has been formed.
A salt is best described as a compound that is formed from the reaction between
an acid and a base.
a strong acid and a weak acid.
a strong base and a weak base.
an acid and water
Save and Exit
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Submit
Answer:
An acid and a Base :)
Explanation:
I just took the test got a 96 A
Consider the following system at equilibrium. CaCO3(s) Ca2+(aq) + CO32–(aq) The addition of which compound will cause a shift in equilibrium because of a common ion effect? CCl4 CO2 CuSO4 Na2CO3
Answer:
Na₂CO₃.
Explanation:
Le Châtelier's principle states that when there is an dynamic equilibrium, and this equilibrium is disturbed by an external factor, the equilibrium will be shifted in the direction that can cancel the effect of the external factor to reattain the equilibrium.The compound that has a common ion effect is Na₂CO₃.
When it is added to the solution, it is dissolved to produce Na⁺ and CO₃²⁻ which increases the concentration of CO₃²⁻ that will increase the concentration of the products side, so the reaction will be shifted to the left side to suppress the increase in the concentration of CO₃²⁻.Answer:
Na2Co3
Explanation:
42.5 grams of an unknown substance is heated to 105.0 degrees Celsius and then placed into a calorimeter containing 110.0 grams of water at 24.2 degrees Celsius. If the final temperature reached in the calorimeter is 32.4 degrees Celsius, what is the specific heat of the unknown substance?
Show or explain the work needed to solve this problem, and remember that the specific heat capacity of water is 4.18 J/(° C × g).
Answer:
The specific heat of the unknown substance is 1.22 J/g.°C.
Explanation:
Knowing that:Heat lost by substance (Qc) = Heat gained by the water (Qw) ,
- (Qc) = (Qw).
We can calculate the amount of heat (Qw) gained by water using the relation:
Qw = m.c.ΔT,
where, Qw is the amount of heat released to water (Q = ??? J).
m is the mass of water (m = 110.0 g).
c is the specific heat capacity of solution (c = 4.18 J/g.°C).
ΔT is the difference in T (ΔT = final temperature - initial temperature = 32.4°C - 24.2°C = 8.2°C).
∴ Q = m.c.ΔT = (110.0 g)(4.18 J/g.°C)(8.2°C) = 3770.36 J.
Now, the amount of heat lost by the substance (Qc) = - 3770.36 J.(Qc) = m.c.ΔT,
where, Qc is the amount of heat lost by substance (Qc = - 3770.36 J).
m is the mass of water (m = 42.5 g).
c is the specific heat capacity of solution (c = ??? J/g.°C).
ΔT is the difference in T (ΔT = final temperature - initial temperature = 32.4°C - 105.0°C = -72.6°C).
∴ (- 3770.36 J) = (42.5 g)(c)(-72.6°C).
∴ c = (- 3770.36 J)/(42.5 g)(-72.6°C) = 1.222 J/g.°C.
Use the collision theory to explain how increasing the temperature of a reaction will affect the rate of the reaction.
Answer:
Explanation:
Reaction rate is a measure of the speed of a chemical reaction. There are many theories that have been put forward to explain reaction rates. One of which is the collision theory.
The collision theory postulates that for a reaction to occur, there must be collisions between reacting particles. This implies that the number of successful or effective collision of particles determines the rate of a chemical reaction. For a collision to be successful, the particles must be properly oriented and equiped with adequate energy for the reaction.
One of the key component of the energy required for effective collision is temeperature. The number of effective collision and consequently the rate of chemical reactions are directly proportional to the temperature at which the reaction occurs. With increasing temperature, the activation energy becomes activated and the number of collision increases.
How does a catalyst speed up a chemical reaction?
Given pH = 8.55 Find: [H3O+] and [OH-] Is this acidic, basic or neutral?
Answer:
Explanation:
The given pH = 8.55
Unknown:
[H₃O⁺] = ?
[OH⁻] = ?
In order to find these unknowns we must first establish some relationship.
pH = -log[H₃O⁺]
8.55 = -log[H₃O⁺]
[H₃O⁺] = inverse log₁₀(-8.55) = 2.82 x 10⁻⁹moldm⁻³
To find the [OH⁻],
pH + pOH = 14
pOH = 14 - pH = 14 - 8.55
pOH = 5.45
pOH = -log[OH⁻]
[OH⁻] = inverse log₁₀ (-5.45) = 3.55 x 10⁻⁶moldm⁻³
The solution is basic because it has more concentration of OH⁻ ions compared to H⁺ ions.
Consider the following intermediate chemical equations.
When you combine the intermediate chemical equations, which substance do you cancel out?
Answer:
PCI3
Explanation:
PCI3 is a product in one reaction and a reactant in the other. This makes it an intermediate as it is produced then used up in the same series of reactions.
Answer: C. PCI3
Explanation:
Gas particles moving through the air due to random motion is called what??
Answer:
Explanation:
In gases the particles move rapidly in all directions, frequently colliding with each other and the side of the container. With an increase in temperature, the particles gain kinetic energy and move faster. ... In liquids, particles are quite close together and move with random motion throughout the container.
Gas particles moving through the air due to random motion is called Brownian motion.
What is Gas ?Gas have no definite volume and gases have not a definite shape it can take the shape of container in which it filled. Gases can flow easily. They are highly compressible. They have low density. Gases have very weak intermolecular force and very large intermolecular space.
What is Brownian Motion ?Brownian motion is also called as Brownian movement is defied as the zig-zag motion of particles suspended in a medium. The gas particles moves randomly in Brownian motion.
Thus from the above conclusion we can say that Gas particles moving through the air due to random motion is called Brownian motion.
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Sarah is asked to sort out the list of ions and ionic compounds. How can Sarah differentiate between the ions and ionic compounds?
Answer:
Ionic compounds differ from ions in that the overall charge in ionic compounds equals zero while the overall charge in ions is less than or greater than zero. Ions have a superscript number followed by a either a positive or a negative sign. Where both signs appear in the same formula they make it an ionic compound.
Consider the following intermediate chemical equations.
CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
2H2O(g) → 2H2O(1)
Which overall chemical equation is obtained by combining these intermediate equations?
CH4(g)+2O2(g) → CO2(g) + 2H2O(1)
CH4(g) +202(g) → CO2(g) + 2H2O(g)
CH4(g) + 2O2(g) → CO2(g) + 4H2O(g) + 2H2O(1)
CH4(g) + 2O2(g) → CO2(g) + 6H2O(g)
Answer:
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l).
Explanation:
We have two equations:CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
2H₂O(g) → 2H₂O(l)
To add the two equations: we omit H₂O(g) that is formed by 2 moles in the product side of the first equation and consumed by 2 moles from the reactants side in the second equationSo, the overall chemical equation is obtained by combining these intermediate equations is:CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l).
Answer: The reaction is Exothermic
CH4(g) + 2O2(g) > CO2(g) + 2H2O(g) + energy
Explanation:
compared to the energy released per mole of reactant during chemical reactions the energy released per mole of reactant during nuclear reactions is
Answer:
[tex]\boxed{\text{Roughly a million times greater}}.[/tex]
Explanation:
For example, the energy released in burning 1 mol of octane, a component of gasoline, is about 5000 kJ.
The energy released in the fission of 1 mol of uranium-235 is
about 1.5 × 10¹⁰ kJ .
The ratio is
[tex]\dfrac{1.5 \times 10^{10} }{5000} \approx 3 \times 10^{6}\\\\\text{The energy released by nuclear reactions is } \boxed{\textbf{roughly a million times greater}}\\\text{ than that released during chemical reactions.}[/tex]
The energy released during chemical reactions is much greater than the energy released per mole of reactant during nuclear reactions.
What is a nuclear reaction?A nuclear reaction can be defined as a type of reaction in which the nucleus of an atom of a radioactive element is transformed by being joined (fusion) or split (fission) with the nucleus of another atom and it is accompanied by the release of great amount if energy.
What is a chemical reaction?A chemical reaction refers to a chemical process that involves the continuous transformation (rearrangement) of the ionic, atomic or molecular structure of a chemical element by breaking down and forming chemical bonds, in order to produce a new chemical compound.
In conclusion, the energy released per mole of reactant during chemical reactions is much greater than the energy released per mole of reactant during nuclear reactions.
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DDT is made from the __ of unsaturated hydrocarbons
Answer:
chlorination
Explanation:
Answer: chlorination
Explanation: DDT is made from the
of unsaturated hydrocarbons.
Carbon atoms can form chains _______ of atoms long.
carbon atoms can form chains thousands of atoms long.
Answer:
thousands
Explanation:
Carbon atoms can form chains thousands of atoms long.
Why is it that 85.48 rounded to two significant figures is 85 and not 86?
Answer:
See below.
Explanation:
That is because of the .48.
85.48 is closer to 85 than 86.
What is the molar mass of CHC13?
Answer:119.38 g/mol
Explanation:
Add the Molar mass of each element to get the final answer. Use the Periodic table to find the molar mass. Molar mass is located under neath the elements.
Molecular mass of CHCl3 is 119.5 grams/mole
What is molecular mass ?It is the sum of atomic weights of all the atoms present in the molecule.How to solve this problem?Mass of Carbon=12 grams / moleMass of Hydrogen=1 gram/moleMass of Chlorine= 35.5 grams/ moleMolecular mass of CHCl3 = mass of Carbon+ mass of Hydrogen+ 3×(mass of Chlorine)
Molecular mass of CHCl3= 12+1+(3×35.5)= 119.5
Hence The Molecular mass of CHCl3 is 119.5 grams/ mole
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PLEASE HELP. Give the orbital configuration of the phosphorus (p) atom.
Answer:
Explanation:
The Electronic Configuration of the elements is the arrangement of all electrons of an element in energy levels and sub-levels (orbitals).
There are 7 energy levels, numbered from 1 to 7, and in which electrons are distributed, logically in order according to their energy level. Each level is divided into sub-levels. These sub-levels into which each level is divided can be up to 4, called: s, p, d, f. In the sub-level s there can only be a maximum of 2 electrons, in p there can be a maximum of 6 electrons, in the sub-level d 10 electrons and finally in the sub-level f there can be a maximum of 14 electrons.
In level 1 there is only one sub-level, which will be the s. In level 2 there are 2 sub-levels, the s and the p. At level 3 there are 3 sub-levels s, p and d. And at level 4 there are 4 sub-levels, the s, the p, the d and the f.
Aufbau's principle is a principle of atomic physics, which explains how electrons are accommodated in their orbits around the nucleus of the atom. This principle states that the filling of these orbitals occurs in increasing order of energy, that is, from the orbitals of lower energy to those of higher energy.
The simplest of the sub-levels is 1s. If you fill the 1s you can start filling the 2s. After the 2s sub-level is satisfied, the 2p can begin to fill and so on.
The atomic number Z of the element represents the number of protons of the element, and in a neutral atom it also indicates the number of electrons.
So, given that the atomic number of the phosphorus is 15, and everything that has been said before, it is possible to say that the electrons that it has in the orbitals will be placed as follows:
1s² 2s² 2p⁶ 3s² 3p³
Finally, the orbital configuration of the phosphorus atom (P) will be as the image shows.
The orbital configuration of the phosphorus (p) atom is attached to the image below.
The phosphorus (P) atom has an atomic number of 15, which means it has 15 electrons. The electron configuration of phosphorus can be determined by filling up the orbitals according to the Aufbau principle and the Pauli exclusion principle.
1s² 2s² 2p⁶ 3s² 3p³, this electron configuration represents the distribution of electrons in the atomic orbitals of a phosphorus atom. The numbers represent the principal quantum numbers (n) and the letters represent the azimuthal quantum numbers (s, p). The superscripts indicate the number of electrons occupying each orbital.
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name 3 cell structures that are found in a plant cell and NOT in an animal cell;
Answer:
cell wall
chloroplasts
central vacuole
Explanation:
Plant cells have a cell wall, chloroplasts, and a central vacuole. These structures are not found in animal cells.
The structures of three cells present in the cells in plant, but not animal cell are Cell wall, Chloroplast and Plastids.
Explanation:Animal cell only contain cell membrane whereas plant cell has both cell wall and cell membrane. Unlike animal cell, plant cell makes their own food. The plants come under autotrophs and animals come under heterotrophs.
For this purpose, there is chloroplast in a plant cell. The major function of chloroplast is to produce food through photosynthesis. Plastids are the pigment containing cell organelles which is responsible for the color of plant cell.
The rock in a lead ore deposit contains 89 % PbS by mass. How many kilograms of the rock must be processed to obtain 1.5 kg of Pb?
Answer:
Approximately 1.9 kilograms of this rock.
Explanation:
Relative atomic mass data from a modern periodic table:
Pb: 207.2;S: 32.06.To answer this question, start by finding the mass of Pb in each kilogram of this rock.
89% of the rock is [tex]\rm PbS[/tex]. There will be 890 grams of [tex]\rm PbS[/tex] in one kilogram of this rock.
Formula mass of [tex]\rm PbS[/tex]:
[tex]M(\mathrm{PbS}) = 207.2 + 32.06 = 239.26\; g\cdot mol^{-1}[/tex].
How many moles of [tex]\rm PbS[/tex] formula units in that 890 grams of [tex]\rm PbS[/tex]?
[tex]\displaystyle n = \frac{m}{M} = \rm \frac{890}{239.26} = 3.71980\; mol[/tex].
There's one mole of [tex]\rm Pb[/tex] in each mole of [tex]\rm PbS[/tex]. There are thus [tex]\rm 3.71980\; mol[/tex] of [tex]\rm Pb[/tex] in one kilogram of this rock.
What will be the mass of that [tex]\rm 3.71980\; mol[/tex] of [tex]\rm Pb[/tex]?
[tex]m(\mathrm{Pb}) = n(\mathrm{Pb}) \cdot M(\mathrm{Pb}) = \rm 3.71980 \times 207.2 = 770.743\; g = 0.770743\; kg[/tex].
In other words, the [tex]\rm PbS[/tex] in 1 kilogram of this rock contains [tex]\rm 0.770743\; kg[/tex] of lead [tex]\rm Pb[/tex].
How many kilograms of the rock will contain enough [tex]\rm PbS[/tex] to provide 1.5 kilogram of [tex]\rm Pb[/tex]?
[tex]\displaystyle \frac{1.5}{0.770743} \approx \rm 1.9\; kg[/tex].