Question 1

Which law is obeyed when a chemical equation is balanced, and what does it require?

Accepted Answer

Law of Conservation of Mass; it requires that the total mass of each element is the same on both sides of the equation.

Question 2

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

Accepted Answer

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

Question 3

When balancing the equation $$\mathrm{C_5H_{12} + O_2$ \rightarrow CO_2$ + H_2O}$$, what is the correct coefficient for $$\mathrm{O_2$}$$?

Accepted Answer

8

Question 4

A graduated cylinder initially contains 32.5 mL of liquid. After removing some, it reads 23.5 mL. If the liquid is $$\mathrm{C$$_{16}$$H_{34}O_3$}$$ with a density of $$0.91\ \mathrm{g/mL}$$, what is the mass of the extracted liquid?

Accepted Answer

$$8.19\ \mathrm{g}$$

Question 5

Given the combustion reaction $$\mathrm{C$$_{16}$$H_{34}O_3$ + 23\ O_2$ \rightarrow 16\ CO_2$ + 17\ H_2O}$$, how many grams of $$\mathrm{O_2$}$$ are required to combust $$9.0\ \mathrm{mL} of$$ $$\mathrm{C$$_{16}$$H_{34}O_3$} ($$density $$0.91\ \mathrm{g/mL}$$, molar mass $$274\ \mathrm{g/mol}$$)?

Accepted Answer

$$22\ \mathrm{g}$$

Question 6

Combustion analysis of $$63.8\ \mathrm{mg} of a $$compound containing only C, H, and O produces $$145.0\ \mathrm{mg}$$ $$\mathrm{CO_2$}$$ and $$59.38\ \mathrm{mg}$$ $$\mathrm{H_2O}. $$What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{C_3H_6O}$$

Question 7

Which of the following best describes a limiting reactant in a chemical reaction?

Accepted Answer

The reactant that determines the amount of product formed.

Question 8

In the reaction $$\mathrm{2H_2 + O_2$ \rightarrow 2H_2O}$$, if you start with $$4$$ moles of $$\mathrm{H_2$}$$ and $$1$$ mole of $$\mathrm{O_2$}$$, which is the limiting reactant?

Accepted Answer

$$\mathrm{O_2$}$$

Question 9

A reaction uses $$2.00\ \mathrm{g} of$$ $$\mathrm{NH_3$} ($$molar mass $$17\ \mathrm{g/mol}) $$and $$4.00\ \mathrm{g} of$$ $$\mathrm{O_2$} ($$molar mass $$32\ \mathrm{g/mol}) to $$form $$\mathrm{NO}$$ and $$\mathrm{H_2O}. $$Which is the limiting reactant?

Accepted Answer

$$\mathrm{O_2$}$$

Question 10

How many moles of $$\mathrm{$$SiF_4$$}$$ are produced from $$4.5$$ mol $$\mathrm{$$SiO_2$$}$$ and $$6.0$$ mol $$\mathrm{HF} in $$the reaction $$\mathrm{$$SiO_2$$ + 4HF \rightarrow $$SiF_4$$ + 2H_2O}$$?

Accepted Answer

$$1.5$$ mol

Question 11

Which of the following is a correct step when balancing a chemical equation?

Accepted Answer

Balance elements that appear in only one reactant and one product first.

Question 12

If $$30\ \mathrm{g} of$$ $$\mathrm{$$SiO_2$$} ($$molar mass $$60\ \mathrm{g/mol}) $$reacts with $$30\ \mathrm{g} of$$ $$\mathrm{HF} ($$molar mass $$20\ \mathrm{g/mol}$$), what is the limiting reactant in the reaction $$\mathrm{$$SiO_2$$ + 4HF \rightarrow $$SiF_4$$ + 2H_2O}$$?

Accepted Answer

$$\mathrm{HF}$$

Question 13

Which of the following best explains why chemical equations must be balanced?

Accepted Answer

To satisfy the law of conservation of mass.

Question 14

In a combustion reaction, what are the typical products when a hydrocarbon reacts with oxygen?

Accepted Answer

$$\mathrm{CO_2$}$$ and $$\mathrm{H_2O}$$

Question 15

A student balances the equation $$\mathrm{$$KNO_3$$ + H_2CO_3 \rightarrow K_2CO_3 + $$HNO_3$$}. $$What are the correct coefficients?

Accepted Answer

2, 1, 1, 2

Question 16

Which of the following is a real-world application of stoichiometry?

Accepted Answer

Calculating the amount of fertilizer needed for a crop based on the chemical reaction of nutrients in soil.

Chemical Reactions, Stoichiometry, and Limiting Reactants

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