Question 1

Which of the following statements best describes the Law of Constant Composition as it applies to water ($$\mathrm{H_2O}$$)?

Accepted Answer

All samples of water contain hydrogen and oxygen in a fixed mass ratio of 8:1.

Question 2

How many total atoms are present in one formula unit of $$\mathrm{Mg(NO_3$)_2}$$?

Accepted Answer

$$\displaystyle 9 (1 Mg$$, 2 N, 6 O)

Question 3

Which of the following is a molecular element?

Accepted Answer

Oxygen gas ($$\mathrm{O_2$})$$

Question 4

Given the reaction: $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$, what type of reaction is this?

Accepted Answer

Combustion

Question 5

If you have 10 grams of hydrogen ($$\mathrm{H}$$, molar mass = 1 g/mol) and 10 grams of boron ($$\mathrm{B}$$, molar mass = 10.8 g/mol), which sample contains more atoms?

Accepted Answer

The hydrogen sample contains more atoms.

Question 6

Which of the following best describes an ionic compound?

Accepted Answer

A compound composed of ions held together by electrostatic forces.

Question 7

What is the molar mass of $$\mathrm{CO_2$}$$?

Accepted Answer

$$\displaystyle 44.01\ \mathrm{g/mol}$$

Question 8

Which abbreviation correctly represents an aqueous solution in a chemical equation?

Accepted Answer

$$(aq)$$

Question 9

A student mixes two clear solutions and observes the formation of a solid. What type of reaction has most likely occurred?

Accepted Answer

Precipitation

Question 10

Which of the following is a diatomic molecule found naturally in the atmosphere?

Accepted Answer

Nitrogen ($$\mathrm{N_2$})$$

Question 11

In the pancake analogy for stoichiometry, if the recipe is $$1$$ cup flour $$+$$ $$2$$ eggs $$+$$ $$\frac{1}{2}$$ tsp baking powder $$= 5$$ pancakes, how many eggs are needed to make $$15$$ pancakes, assuming you have enough of the other ingredients?

Accepted Answer

$$\displaystyle 6$$

Question 12

Which of the following best describes an exothermic reaction?

Accepted Answer

A reaction that releases heat to the surroundings.

Question 13

Which of the following is the correct empirical formula for glucose ($$\mathrm{C_6H_{12}O_6$}$$)?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 14

Which of the following is NOT evidence that a chemical reaction has occurred?

Accepted Answer

A change in state from solid to liquid due to heating.

Question 15

If you have $$3$$ cups of flour, $$4$$ eggs, and $$1.5$$ tsp of baking powder, and the recipe is $$1$$ cup flour $$+$$ $$2$$ eggs $$+$$ $$\frac{1}{2}$$ tsp baking powder $$= 5$$ pancakes, what is the theoretical yield of pancakes?

Accepted Answer

$$\displaystyle 15$$

Question 16

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 17

Which of the following is true about balancing chemical equations?

Accepted Answer

You can only change the coefficients in front of chemical formulas.

Question 18

Which of the following is an example of a single-displacement reaction?

Accepted Answer

$$\mathrm{A + BC \rightarrow AC + B}$$

Question 19

What is Avogadro’s number?

Accepted Answer

$$\displaystyle 6.022 	imes 10$$^{23}$$

Question 20

Which of the following best describes a net ionic equation?

Accepted Answer

An equation that shows only the species that actually participate in the reaction.

CH100 Exam 2 Study Guide: Molecules, Compounds, Chemical Composition, Reactions, and Quantities

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