Question 1

How many molecules are in a sample of water, H2O, which has a mass of 50.0 g?

Accepted Answer

A)  1.67 x 1024 molecules
B)  5.42 x 1026 molecules
C)  2.16 x 1023 molecules
D)  3.01 x 1025 molecules
E)  8.30 x 10-23 moleculesF) A) and D)
G) C) and D)

Question 2

Calculate the molar mass of PH3.

Accepted Answer

A)  40.11 g/mol
B)  31.98 g/mol
C)  33.99 g/mol
D)  93.92 g/mol
E)  2.05 x 1025 g/molF) A) and B)
G) C) and D) C

Question 3

If the molar mass of a substance is 20.0 g/mol, what is the mass of 4.01 x 1023 molecules of the substance?

Accepted Answer

A)  30.0 g
B)  13.3 g
C)  8.02 x 1024 g
D)  1.20 x 1025 g
E)  3.00 gF) D) and E)
G) C) and D)

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 F) A) and C)
G) B) and D)

Question 5

If the molar mass of a substance is 44.01 g/mol, what is the mass of 1.05 x 1024 molecules of the substance?

Accepted Answer

A)  76.7 g
B)  1.74 g
C)  4.62 x 1025 g
D)  4.19 x 10-23 g
E)  25.2 gF) C) and D)
G) A) and E)

Question 6

Which of the molecules in the figure have an empirical formula that is different from their molecular formula? 2O2, N2O4, and HCO2H B) SiO2  C) H2O2 and N2O4  D) all of the compounds E) none of the compounds" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)  H2O2, N2O4, and HCO2H
B)  SiO2 
C)  H2O2 and N2O4 
D)  all of the compounds
E)  none of the compoundsF) A) and E)
G) A) and B) C

Question 7

Calculate the molar mass of C3H6Cl2.

Accepted Answer

A)  155.08 g/mol
B)  77.54 g/mol
C)  48.47 g/mol
D)  72.49 g/mol
E)  112.98 g/molF) B) and C)
G) A) and B)

Question 8

How much water had to be added to 10.0 mL of the first solution to obtain the second solution?

Accepted Answer

A)  10.0 mL
B)  20.0 mL
C)  40.0 mL
D)  50.0 mL
E)  500.0 mLF) A) and B)
G) B) and E)

Question 9

5.06 moles of iron(II)  phosphate, Fe3(PO4) 2, are produced in a reaction.What mass of iron(II)  phosphate is produced?

Accepted Answer

A)  520.g
B)  20.3 g
C)  1.81 x 103 g
D)  3.05 x 1024 g
E)  70.7 gF) None of the above
G) A) and B)

Question 10

A 100.0 g sample of a compound contains 1.37 x 1024 molecules.Which of the following could be this compound?

Accepted Answer

A)  CO2 
B)  NH3 
C)  CH4 
D)  CCl4 
E)  CF4 F) A) and B)
G) A) and E)

Question 11

How many molecules of CO2 are present in 0.100 mol of CO2?

Accepted Answer

A)  6.02 x 1022 molecules
B)  4.40 molecules
C)  1.66 x 10-25 molecules
D)  6.02 x 1024 molecules
E)  0.100 moleculesF) A) and B)
G) B) and D)

Question 12

If 50.0 mL of 0.235 M NaCl solution is diluted to 200.0 mL, what is the concentration of the diluted solution?

Accepted Answer

A)  0.0588 M
B)  0.0118 M
C)  58.8 M
D)  1.18 M
E)  0.0426 MF) A) and C)
G) A) and B)

Question 13

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

Accepted Answer

A)  2.5
B)  7.5
C)  1.5 x 1024 
D)  4.5 x 1024 
E)  4.2 x 10-24 F) A) and C)
G) A) and B)

Question 14

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% OF) A) and B)
G) A) and E)

Question 15

How many hydrogen atoms are there in 2.0 moles of CH4?

Accepted Answer

A)  8.0
B)  2.0
C)  1.2 x 1024 
D)  1.3 x 10-23 
E)  4.8 x 1024 F) None of the above
G) A) and D)

Question 16

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 F) A) and B)
G) A) and C)

Question 17

Rank the substances in the figure from least atoms per mole to most atoms per mole. 2 2H6 2 2H6 2 = CO2 2 = SiO2 2H6  D) Fe 2 2 2H6  E) C2H6 2 2

Accepted Answer

A)  SiO2 2H6 2 
B)  C2H6 2 = CO2 
C)  Fe 2 = SiO2 2H6 
D)  Fe 2 2 2H6 
E)  C2H6 2 2 < FeF) A) and B)
G) A) and C) C

Question 18

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.F) A) and B)
G) A) and C)

Question 19

A chemical reaction produces 7.25 moles of barium sulfate, BaSO4.What mass of barium sulfate is produced?

Accepted Answer

A)  185 g
B)  233 g
C)  1.69 x 103 g
D)  31.1 g
E)  3.11 x 10-2 gF) All of the above
G) B) and C)

Question 20

Which of the following statements regarding atoms, molecules, and moles is correct?

Accepted Answer

A)  Chemists are inherently lazy, so they weigh substances in order to avoid counting out the atoms or molecules in a sample.
B)  It would be possible for an individual to count out a mole of atoms or molecules if they had a few days to do it.
C)  A single grain of sand has about as many formula units of SiO2 as there are sand grains on all of the beaches on Earth.
D)  A mole of HCl would have the same mass as a mole of NaCl, since they have the same number of particles.
E)  Since a mole of LiCl has a mass of 42.39 g, the average mass of a LiCl formula unit would be 42.39 mole.F) A) and B)
G) B) and C)

Exam 4: Chemical Composition

How many molecules are in a sample of water, H2O, which has a mass of 50.0 g?

Correct AnswerverifiedShow Answer

Calculate the molar mass of PH3.

Correct AnswerverifiedC

If the molar mass of a substance is 20.0 g/mol, what is the mass of 4.01 x 1023 molecules of the substance?

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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 44.01 g/mol, what is the mass of 1.05 x 1024 molecules of the substance?

Correct AnswerverifiedShow Answer

Which of the molecules in the figure have an empirical formula that is different from their molecular formula?

Correct AnswerverifiedC

Calculate the molar mass of C3H6Cl2.

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How much water had to be added to 10.0 mL of the first solution to obtain the second solution?

Correct AnswerverifiedShow Answer

5.06 moles of iron(II) phosphate, Fe3(PO4) 2, are produced in a reaction.What mass of iron(II) phosphate is produced?

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A 100.0 g sample of a compound contains 1.37 x 1024 molecules.Which of the following could be this compound?

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How many molecules of CO2 are present in 0.100 mol of CO2?

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If 50.0 mL of 0.235 M NaCl solution is diluted to 200.0 mL, what is the concentration of the diluted solution?

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

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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 hydrogen atoms are there in 2.0 moles of CH4?

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

Correct AnswerverifiedC

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

Correct AnswerverifiedShow Answer

A chemical reaction produces 7.25 moles of barium sulfate, BaSO4.What mass of barium sulfate is produced?

Correct AnswerverifiedShow Answer

Which of the following statements regarding atoms, molecules, and moles is correct?

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How many molecules are in a sample of water, H₂O, which has a mass of 50.0 g?

Correct Answer
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Calculate the molar mass of PH₃.

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C

If the molar mass of a substance is 20.0 g/mol, what is the mass of 4.01 x 10²³ molecules of the substance?

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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 44.01 g/mol, what is the mass of 1.05 x 10²⁴ molecules of the substance?

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C

Calculate the molar mass of C₃H₆Cl₂.

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5.06 moles of iron(II) phosphate, Fe₃(PO₄) ₂, are produced in a reaction.What mass of iron(II) phosphate is produced?

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A 100.0 g sample of a compound contains 1.37 x 10²⁴ molecules.Which of the following could be this compound?

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How many molecules of CO₂ are present in 0.100 mol of CO₂?

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

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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 hydrogen atoms are there in 2.0 moles of CH₄?

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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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C

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A chemical reaction produces 7.25 moles of barium sulfate, BaSO₄.What mass of barium sulfate is produced?

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