Question 1

Which law is violated if a chemical equation is not balanced, such as $$\mathrm{CH_4$(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g)}$$ before balancing?

Accepted Answer

Law of Conservation of Mass

Question 2

Given the unbalanced equation $$\mathrm{C_2H_6(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g)}$$, what are the correct coefficients when the equation is balanced?

Accepted Answer

$$2\mathrm{C_2H_6(g)} + 7\mathrm{O_2$(g)} \rightarrow 4\mathrm{CO_2$(g)} + 6\mathrm{H_2O(g)}$$

Question 3

Which of the following best describes a precipitation reaction?

Accepted Answer

A reaction in which dissolved substances react to form one or more solid products

Question 4

What is the net ionic equation for the reaction between $$\mathrm{NaCl(aq)}$$ and $$\mathrm{$$AgNO_3$$(aq)}$$?

Accepted Answer

$$\mathrm{Ag^+(aq) + Cl^-(aq) \rightarrow AgCl(s)}$$

Question 5

Which of the following compounds is insoluble in water and will form a precipitate when mixed with a solution containing $$\mathrm{Cl^-}$$ ions?

Accepted Answer

$$\mathrm{$$AgNO_3$$}$$

Question 6

Which of the following is the correct net ionic equation for the reaction between $$\mathrm{KI(aq)}$$ and $$\mathrm{Pb(NO_3$)_2(aq)}$$?

Accepted Answer

$$2\mathrm{I^-}(aq) + \mathrm{Pb$$^{2+}$$}(aq) \rightarrow \mathrm{$$PbI_2$$}(s)$$

Question 7

Which of the following best describes a strong acid?

Accepted Answer

An acid that completely ionizes in water to produce hydronium ions

Question 8

What is the balanced net ionic equation for the neutralization of hydrochloric acid with sodium hydroxide?

Accepted Answer

$$\mathrm{H^+(aq) + OH^-(aq) \rightarrow H_2O(l)}$$

Question 9

Which of the following is a polyprotic acid?

Accepted Answer

$$\mathrm{H_2SO_4}$$

Question 10

Which of the following is the correct dissociation equation for $$\mathrm{Ba(OH)_2} in $$water?

Accepted Answer

$$\mathrm{Ba(OH)_2(aq) \rightarrow Ba$$^{2+}$$(aq) + 2OH^-(aq)}$$

Question 11

In the reaction $$2\mathrm{Na(s)} + \mathrm{Cl_2$(g)} \rightarrow 2\mathrm{NaCl(s)}$$, which species is oxidized and which is reduced?

Accepted Answer

Na is oxidized, Cl$$_2 is $$reduced

Question 12

Which of the following is the correct half-reaction for the reduction of chlorine gas in the reaction $$2\mathrm{Na(s)} + \mathrm{Cl_2$(g)} \rightarrow 2\mathrm{NaCl(s)}$$?

Accepted Answer

$$\mathrm{Cl_2$(g) + 2e^- \rightarrow 2Cl^-(s)}$$

Question 13

A sample of 0.4550 g of a mixture containing $$\mathrm{$$MgSO_4$$} is $$dissolved in water and treated with excess $$\mathrm{Ba(NO_3$)_2}$$, resulting in the precipitation of 0.6168 g of $$\mathrm{$$BaSO_4$$}. $$What is the mass percent of $$\mathrm{$$MgSO_4$$} in $$the original mixture? (Molar masses: $$\mathrm{$$BaSO_4$$} = 233.39 g/$$mol, $$\mathrm{$$MgSO_4$$} = 120.37 g/$$mol)

Accepted Answer

50.7%

Question 14

If 2.2 $$	imes$$ $$10^{12} kg of $$methane ($$\mathrm{CH_4$}) is $$burned in a year, how many kilograms of carbon dioxide ($$\mathrm{CO_2$}) $$are released? (Molar mass $$\mathrm{CH_4$} = 16.04 g/$$mol, $$\mathrm{CO_2$} = 44.01 g/$$mol)

Accepted Answer

6.0 $$	imes$$ $$10^{12} kg$$

Question 15

A hydrocarbon is combusted with 18.21 g of $$\mathrm{O_2$} to $$yield 23.11 g of $$\mathrm{CO_2$}$$ and 4.73 g of $$\mathrm{H_2O}. $$What is the empirical formula of the hydrocarbon?

Accepted Answer

$$\mathrm{C_3H_8}$$

Question 16

Which of the following statements about limiting reactants is correct?

Accepted Answer

The limiting reactant is completely consumed first and determines the maximum amount of product formed.

Question 17

A reaction has a theoretical yield of 10.0 g, but only 7.5 g of product is actually obtained. What is the percent yield?

Accepted Answer

75%

Question 18

Which of the following is the correct net ionic equation for the neutralization of $$\mathrm{H_2SO_4}$$ with $$\mathrm{Ba(OH)_2}$$?

Accepted Answer

$$2\mathrm{H^+(aq)} + 2\mathrm{OH^-(aq)} \rightarrow 2\mathrm{H_2O(l)}$$

Stoichiometry of Chemical Reactions: Writing, Balancing, and Classifying Equations

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