Question 1

Which of the following statements best describes the law of conservation of mass as it applies to chemical reactions?

Accepted Answer

Atoms are neither created nor destroyed; the total mass of reactants equals the total mass of products.

Question 2

Given the unbalanced chemical equation: $$\mathrm{C_3H_8} + \mathrm{O_2$} \rightarrow \mathrm{CO_2$} + \mathrm{H_2O}$$, what is the correct coefficient for $$\mathrm{O_2$}$$ when the equation is balanced?

Accepted Answer

5

Question 3

Which of the following is the correct balanced chemical equation for the reaction of sodium hydroxide with hydrochloric acid?

Accepted Answer

$$\mathrm{NaOH} + \mathrm{HCl} \rightarrow \mathrm{NaCl} + \mathrm{H_2O}$$

Question 4

In the reaction $$\mathrm{Al} + \mathrm{Co(NO_3$)_2} \rightarrow \mathrm{Al(NO_3$)_3} + \mathrm{Co}$$, what is the stoichiometric coefficient for aluminum when the equation is balanced using the lowest whole numbers?

Accepted Answer

2

Question 5

Which physical state symbol is used to represent a substance dissolved in water in a chemical equation?

Accepted Answer

$$(aq)$$

Question 6

A sample problem asks: 'What mass of $$\mathrm{O_2$}$$ will react with 96.1 g of propane ($$\mathrm{C_3H_8}$$)?' After converting grams of propane to moles, what is the next step?

Accepted Answer

Balance the chemical equation.

Question 7

Which of the following is true about the coefficients in a balanced chemical equation?

Accepted Answer

They represent the relative minimum number of molecules or moles needed for a reaction to occur.

Question 8

In the reaction $$4\mathrm{NO_2$} (g) + \mathrm{O_2$} (g) + 2\mathrm{H_2O} (l) \rightarrow 4\mathrm{$$HNO_3$$} (aq)$$, if 16 kg of $$\mathrm{NO_2$} is $$used, what is the mass of $$\mathrm{$$HNO_3$$}$$ produced, assuming excess $$\mathrm{O_2$}$$ and $$\mathrm{H_2O}$$? (Molar masses: $$\mathrm{NO_2$} = 46 g/$$mol, $$\mathrm{$$HNO_3$$} = 63 g/$$mol)

Accepted Answer

21.9 kg

Question 9

Which of the following steps is NOT part of the systematic approach to balancing a chemical equation?

Accepted Answer

Change the chemical formulas of reactants or products to achieve balance.

Question 10

Radium phosphate reacts with sulfuric acid to form radium sulfate and phosphoric acid. What is the coefficient for sulfuric acid when the equation is balanced using the lowest whole numbers?

Accepted Answer

2

Question 11

Which of the following best describes a product in a chemical reaction?

Accepted Answer

A substance formed and present on the right side of the arrow in a chemical equation.

Question 12

If 2.18 moles of $$\mathrm{C_3H_8}$$ react completely with $$\mathrm{O_2$}$$, how many moles of $$\mathrm{CO_2$}$$ are produced? (Balanced equation: $$\mathrm{C_3H_8} + 5\mathrm{O_2$} \rightarrow 3\mathrm{CO_2$} + 4\mathrm{H_2O})$$

Accepted Answer

6.54 moles

Question 13

Which of the following is the correct mole ratio between $$\mathrm{NO_2$}$$ and $$\mathrm{$$HNO_3$$} in $$the reaction $$4\mathrm{NO_2$} + \mathrm{O_2$} + 2\mathrm{H_2O} \rightarrow 4\mathrm{$$HNO_3$$}$$?

Accepted Answer

1:1

Question 14

Which of the following is a correct statement about reactants in a chemical equation?

Accepted Answer

Reactants are substances that are consumed during the reaction.

Question 15

When balancing the equation $$\mathrm{H_2$} + \mathrm{O_2$} \rightarrow \mathrm{H_2O}$$, what is the correct set of coefficients?

Accepted Answer

2, 1, 2

Question 16

Which of the following is the correct physical state symbol for water vapor in a chemical equation?

Accepted Answer

$$(g)$$

Question 17

If you are given the mass of a reactant and asked to find the mass of a product in a chemical reaction, which step must you perform first after writing and balancing the equation?

Accepted Answer

Convert the mass of the reactant to moles.

Question 18

Which of the following is NOT a correct guideline for balancing chemical equations?

Accepted Answer

Change the subscripts in chemical formulas to balance atoms.

Question 19

Which of the following is the correct balanced equation for the combustion of methane?

Accepted Answer

$$\mathrm{CH_4$} + 2\mathrm{O_2$} \rightarrow \mathrm{CO_2$} + 2\mathrm{H_2O}$$

Chemical Equations and Stoichiometry: Writing, Balancing, and Calculations

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