Q: Which statement about the mole is correct?

A mole is the amount of a substance that contains $$6.02 \times 10$$^{23}$$ particles.

Question 1

Which of the following best describes the purpose of balancing a chemical equation?

Accepted Answer

To ensure the same number of atoms of each element are present on both sides of the equation.

Question 2

A landslide in El Yunque National Forest exposes minerals to air and water. Which chemical reaction is most likely to occur as a result, helping to control climate long-term?

Accepted Answer

Minerals react with CO$$_2$$ dissolved in water to form carbonates.

Question 3

Which of the following is the correct balanced equation for the deployment of an airbag, where sodium azide decomposes?

Accepted Answer

$$2 \mathrm{NaN}_3 \rightarrow 2 \mathrm{Na} + 3 \mathrm{N}_2$$

Question 4

Which statement about the mole is correct?

Accepted Answer

A mole is the amount of a substance that contains $$6.02 	imes 10$$^{23}$$ particles.

Question 5

At standard temperature and pressure (STP), what is the volume occupied by one mole of any gas?

Accepted Answer

$$22.4 L$$

Question 6

Which of the following is NOT a correct step in a stoichiometric calculation?

Accepted Answer

Change the subscripts in the chemical formula to balance the equation.

Question 7

In the reaction $$\mathrm{CH}_4 + 2 \mathrm{O}_2 \rightarrow \mathrm{CO}_2 + 2 \mathrm{H}_2\mathrm{O}$$, how many moles of water are produced from 1 mole of methane?

Accepted Answer

2 moles

Question 8

Which of the following best explains Avogadro’s hypothesis?

Accepted Answer

Volumes of all gases contain the same number of molecules when measured at the same temperature and pressure.

Question 9

A student is asked to balance the equation $$\mathrm{H}_2 + \mathrm{O}_2 \rightarrow \mathrm{H}_2\mathrm{O}. $$Which is the correct balanced equation?

Accepted Answer

$$2 \mathrm{H}_2 + \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O}$$

Question 10

If you have 44 grams of CO$$_2 ($$molar mass = 44 g/mol), how many moles of CO$$_2 do $$you have?

Accepted Answer

1 mole

Question 11

In the reaction $$3 \mathrm{H}_2 + \mathrm{N}_2 \rightarrow 2 \mathrm{NH}_3$$, what is the ratio of hydrogen gas to ammonia gas by volume at STP?

Accepted Answer

3:2

Question 12

Which of the following is a correct interpretation of the coefficients in a balanced chemical equation?

Accepted Answer

They represent the number of moles of each substance.

Question 13

A chemical equation uses (aq) to denote a species. What does (aq) mean?

Accepted Answer

Aqueous solution

Question 14

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

Accepted Answer

Calculating the amount of fertilizer needed for a field based on the chemical reaction of nitrogen fixation.

Question 15

Which of the following is NOT a correct way to balance a chemical equation?

Accepted Answer

Changing the subscripts in the chemical formulas.

Question 16

If you start with 2 moles of H$$_2$$ and 1 mole of O$$_2$$, how many moles of H$$_2O $$will be produced according to the equation $$2 \mathrm{H}_2 + \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O}$$?

Accepted Answer

2 moles

Question 17

Which of the following best describes the law of combining volumes?

Accepted Answer

The volumes of gaseous reactants and products are in small whole-number ratios when measured at the same temperature and pressure.

Question 18

Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

Accepted Answer

$$	ext{moles} = \frac{	ext{mass (g)}}{	ext{molar mass (g/mol)}}$$

Question 19

Which of the following is a correct statement about chemical equations?

Accepted Answer

Chemical equations use symbols and formulas to represent the elements and compounds involved in a reaction.

Question 20

If a reaction produces 3 moles of N$$_2$$ from sodium azide, how many moles of Na are produced according to the balanced equation $$2 \mathrm{NaN}_3 \rightarrow 2 \mathrm{Na} + 3 \mathrm{N}_2$$?

Accepted Answer

2 moles

Lecture 13

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