Question 1

Calculate the molar mass of Na2SO4.

Accepted Answer

A)  94.05 g/mol
B)  71.06 g/mol
C)  119.06 g/mol
D)  142.04 g/mol
E)  110.05 g/mol

Question 2

A 6.25 g sample of magnetite (Fe3O4) contains 4.52 g of Fe. What are the percentages of iron and oxygen in magnetite?

Accepted Answer

A)  28.6% Fe and 71.4% O
B)  42.8% Fe and 57.2% O
C)  72.3% Fe and 27.7% O
D)  27.7% Fe and 72.3% O
E)  57.2% Fe and 42.8% O

Question 3

To obtain 0.50 moles of potassium nitrate from a solution, you could either use 100.0 mL of a 5.0 M solution, or 250.0 mL of a 2.0 M solution.

Accepted Answer

A) True 
 B)False

Question 4

Rank the following compounds in order from least chlorine atoms to most chlorine atoms in a 50.0 g sample: Cl2, ClF3, Cl2O, PCl3

Accepted Answer

A)  ClF3 2O 2 3
B)  PCl3 2O 2 3
C)  ClF3 3 2O 2
D)  ClF3 3 2 2O
E)  Cl2O 2 3 3

Question 5

Given the following molecular formulas, determine the empirical formula of each compound: P4O10, SnCl2, N2O3, CH3CO2H.

Accepted Answer

A)  P2O5, SnCl2, N2O3, CH3CO2H
B)  PO2.5, SnCl2, N2O3, CH3CO2H
C)  P2O5, SnCl2, N2O3, CH2O
D)  PO2.5, SnCl, NO1.5, CH3CO2H
E)  P4O10, SnCl4, N2O3, CH2O

Question 6

Molarity is defined as the moles of solute divided by the liters of solvent.

Accepted Answer

A) True 
 B)False

Question 7

Rank the following in order of increasing mass: 1.0 mole of methane (CH4) , 0.50 mole of water (H2O) , 0.20 mole of Fe, and 0.010 mole of U.

Accepted Answer

A)  U 2O 4
B)  H2O 4 
C)  H2O 4 
D)  U 2O 4 
E)  U 2O 4

Question 8

What is the mass of 3.5 × 1023 molecules of CO2?

Accepted Answer

A)  1.7 g
B)  26 g
C)  0.58 g
D)  75 g
E)  1.5 × 1025 g

Question 9

How many oxygen atoms are there in 0.25 mole of CO2?

Accepted Answer

A)  0.50
B)  0.25
C)  3.0 × 1023
D)  1.5 × 1023
E)  4.2 × 10−25

Question 10

Calculate the molar mass of HCl.

Accepted Answer

A)  36.46 g/mol
B)  13.02 g/mol
C)  2.196 × 1025 g/mol
D)  6.054 × 10-23 g/mol
E)  72.92 g/mol

Question 11

Calculate the molarity of a solution consisting of 65.5 g of K2SO4 in 5.00 L of solution.

Accepted Answer

A)  3.81 × 103 M
B)  0.250 M
C)  0.0752 M
D)  0.376 M
E)  0.125 M

Question 12

How many formula units are there in 2.5 moles of MgCl2?

Accepted Answer

A)  2.5
B)  7.5
C)  1.5 × 1024
D)  4.5 × 1024
E)  4.2 × 10−24

Question 13

A 5.05 g sample of quartz (SiO2) contains 2.36 g of silicon. What are the percentages of silicon and oxygen in quartz?

Accepted Answer

A)  53.3% Si and 46.7% O
B)  46.7% Si and 53.3% O
C)  29.9% Si and 70.1% O
D)  70.1% Si and 29.9% O
E)  46.7% Si, and insufficient information to calculate % O

Question 14

Which of the following sets of formulas is correct for the molecules in the figure? 2SO3, SCl5, C2H5 B) H2SO4, SCl5, C2H5 C) H2SO4, SCl6, C2H6 D) H2SO4, SCl6, CH6 E) H2SO3, SCl6, C2H6" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)  H2SO3, SCl5, C2H5
B)  H2SO4, SCl5, C2H5
C)  H2SO4, SCl6, C2H6
D)  H2SO4, SCl6, CH6
E)  H2SO3, SCl6, C2H6

Question 15

If the molar mass of a substance is 20.0 g/mol, what is the mass of 3.01 × 1025 molecules of the substance?

Accepted Answer

A)  0.400 g
B)  10.0 g
C)  1.00 × 103 g
D)  6.02 × 1026 g
E)  1.20 × 1025 g

Question 16

Which of the following statements regarding empirical formulas, molecular formulas, and percent composition is correct?

Accepted Answer

A)  The compounds NO2 and N2O4 have the same empirical formula.
B)  The compounds NO2 and N2O4 have the same molecular formula.
C)  The empirical formula of H2O2 is H2O.
D)  The empirical formula of N2O5 is NO2.5.
E)  The compounds PCl3 and PCl5 would have the same percent composition.

Question 17

Which of the following statements regarding empirical and molecular formulas is correct?

Accepted Answer

A)  Information on percent composition is all that is necessary to determine both an empirical and a molecular formula.
B)  A compound with an empirical formula of CH2O and a molar mass of 90 g/mol would have a molecular formula of C3H6O3.
C)  The compounds C2H4 and C3H6 have different empirical formulas.
D)  The formula Ca2Cl4 is the correct empirical formula for calcium chloride.
E)  The compound benzene has a molecular formula of C6H6, so its empirical formula would be C3H3.

Question 18

Calculate the number of moles provided by 50.0 mL of 3.00 M NaOH solution.

Accepted Answer

To calculate the number of moles of NaOH...

Question 19

Calculate the moles and the mass of solute in 250.0 mL of 6.00 M NaOH.

Accepted Answer

A)  6.00 moles and 240.
B)  1.50 moles and 60.0 g
C)  1.50 moles and 0.0375 g
D)  6.00 moles and 0.0150 g
E)  24.0 moles and 0.600 g

Question 20

Rank the substances in the figure from least atoms per mole to most atoms per mole. 3 2SO4 3 2SO4 C) Na 2SO4 3 D) NaCl 3 2SO4 E) H2SO4 3

Accepted Answer

A)  SO3 2SO4 
B)  Na 3 2SO4
C)  Na 2SO4 3
D)  NaCl 3 2SO4
E)  H2SO4 3 < NaCl < Na

Exam 4: Chemical Composition

Which of the following sets of formulas is correct for the molecules in the figure?

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Molarity is defined as the moles of solute divided by the liters of solvent.

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Which of the following statements regarding empirical formulas, molecular formulas, and percent composition is correct?

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How many formula units are there in 2.5 moles of MgCl2?

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Calculate the moles and the mass of solute in 250.0 mL of 6.00 M NaOH.

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What is the mass of 3.5 × 1023 molecules of CO2?

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Rank the following compounds in order from least chlorine atoms to most chlorine atoms in a 50.0 g sample: Cl2, ClF3, Cl2O, PCl3

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If the molar mass of a substance is 20.0 g/mol, what is the mass of 3.01 × 1025 molecules of the substance?

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Given the following molecular formulas, determine the empirical formula of each compound: P4O10, SnCl2, N2O3, CH3CO2H.

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Calculate the molarity of a solution consisting of 65.5 g of K2SO4 in 5.00 L of solution.

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Which of the following statements regarding empirical and molecular formulas is correct?

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Rank the substances in the figure from least atoms per mole to most atoms per mole.

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To obtain 0.50 moles of potassium nitrate from a solution, you could either use 100.0 mL of a 5.0 M solution, or 250.0 mL of a 2.0 M solution.

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A 5.05 g sample of quartz (SiO2) contains 2.36 g of silicon. What are the percentages of silicon and oxygen in quartz?

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Calculate the molar mass of HCl.

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Calculate the molar mass of Na2SO4.

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Calculate the number of moles provided by 50.0 mL of 3.00 M NaOH solution.

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How many oxygen atoms are there in 0.25 mole of CO2?

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Rank the following in order of increasing mass: 1.0 mole of methane (CH4) , 0.50 mole of water (H2O) , 0.20 mole of Fe, and 0.010 mole of U.

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A 6.25 g sample of magnetite (Fe3O4) contains 4.52 g of Fe. What are the percentages of iron and oxygen in magnetite?

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How many formula units are there in 2.5 moles of MgCl₂?

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What is the mass of 3.5 × 10²³ molecules of CO₂?

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Rank the following compounds in order from least chlorine atoms to most chlorine atoms in a 50.0 g sample: Cl₂, ClF₃, Cl₂O, PCl₃

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If the molar mass of a substance is 20.0 g/mol, what is the mass of 3.01 × 10²⁵ molecules of the substance?

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Given the following molecular formulas, determine the empirical formula of each compound: P₄O₁₀, SnCl₂, N₂O₃, CH₃CO₂H.

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Calculate the molarity of a solution consisting of 65.5 g of K₂SO₄ in 5.00 L of solution.

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A 5.05 g sample of quartz (SiO₂) contains 2.36 g of silicon. What are the percentages of silicon and oxygen in quartz?

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Calculate the molar mass of Na₂SO₄.

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To calculate the number of moles of NaOH...
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How many oxygen atoms are there in 0.25 mole of CO₂?

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Rank the following in order of increasing mass: 1.0 mole of methane (CH₄) , 0.50 mole of water (H₂O) , 0.20 mole of Fe, and 0.010 mole of U.

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A 6.25 g sample of magnetite (Fe₃O₄) contains 4.52 g of Fe. What are the percentages of iron and oxygen in magnetite?

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