Question 1

Which law states that the total mass of substances present after a chemical reaction is the same as the total mass of substances before the reaction?

Accepted Answer

Law of Conservation of Mass

Question 2

What is the balanced chemical equation for the combustion of methane ($$\mathrm{CH_4$}) in $$oxygen?

Accepted Answer

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

Question 3

Which of the following best describes the difference between a coefficient and a subscript in a chemical equation?

Accepted Answer

A coefficient changes the amount of molecules, while a subscript changes the composition and identity.

Question 4

Given the reaction $$\mathrm{O_2$ + 2NO \rightarrow 2NO_2}$$, how many nitrogen and oxygen atoms are present on each side of the balanced equation?

Accepted Answer

2 N, 4 O on both sides

Question 5

Which of the following is a decomposition reaction?

Accepted Answer

$$\mathrm{$$CaCO_3$$(s) \rightarrow CaO(s) + CO_2$(g)}$$

Question 6

A sample of ethane ($$\mathrm{C_2H_6}) $$has a molecular weight of 30.070 amu. What is the percent by mass of carbon in ethane?

Accepted Answer

79.9%

Question 7

How many oxygen atoms are present in 0.25 mol of $$\mathrm{Ca(NO_3$)_2}$$?

Accepted Answer

$$9.0 	imes 10$$^{23}$$

Question 8

What is the empirical formula of a compound that contains 40.92% C, 4.58% H, and 54.50% O by mass?

Accepted Answer

$$\mathrm{C_3H_4O_3}$$

Question 9

A 5.23 g sample of glucose ($$\mathrm{C_6H_{12}O_6$}) $$contains how many molecules of glucose?

Accepted Answer

$$1.75 	imes 10$$^{22}$$

Question 10

Which of the following is the correct sequence for converting grams of a substance to the number of formula units?

Accepted Answer

Grams $$\rightarrow$$ Molar Mass $$\rightarrow$$ Moles $$\rightarrow$$ Avogadro's Number $$\rightarrow$$ Formula Units

Question 11

If 1.00 g of lithium hydroxide ($$\mathrm{LiOH}) $$reacts with carbon dioxide ($$\mathrm{CO_2$}) $$according to $$2\mathrm{LiOH(s) + CO_2$(g) \rightarrow Li_2CO_3(s) + H_2O(l)}$$, how many grams of $$\mathrm{CO_2$}$$ can be absorbed?

Accepted Answer

0.919 g

Question 12

In the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightarrow 2NH_3(g)}$$, if you start with 3.0 mol of $$\mathrm{N_2$}$$ and 6.0 mol of $$\mathrm{H_2$}$$, what is the limiting reactant and how many moles of $$\mathrm{NH_3$}$$ can be formed?

Accepted Answer

$$\mathrm{H_2$} is $$limiting, 4.0 mol $$\mathrm{NH_3$}$$

Question 13

A reaction has a theoretical yield of 43.5 g of product, but only 33.5 g is actually obtained. What is the percent yield?

Accepted Answer

77.0\%

Question 14

Which of the following best describes a combustion reaction?

Accepted Answer

A reaction where a hydrocarbon reacts with oxygen to produce carbon dioxide and water.

Question 15

A compound is found to contain 61.31% C, 5.14% H, 10.21% N, and 23.33% O by mass. What is its empirical formula?

Accepted Answer

$$\mathrm{C_7H_7NO_2}$$

Question 16

Which of the following is the correct molar mass for calcium nitrate, $$\mathrm{Ca(NO_3$)_2}$$?

Accepted Answer

164.1 g/mol

Question 17

If 1.00 g of glucose ($$\mathrm{C_6H_{12}O_6$}) is $$oxidized according to $$\mathrm{C_6H_{12}O_6$(s) + 6 O_2$(g) \rightarrow 6 CO_2$(g) + 6 H_2O(l)}$$, how many grams of water are produced?

Accepted Answer

0.600 g

Question 18

Which of the following is true about the limiting reactant in a chemical reaction?

Accepted Answer

It is the reactant that is completely consumed first, limiting the amount of product formed.

Stoichiometry: Calculations with Chemical Formulas and Equations

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