Q: How many molecules are present in 2.50 moles of glucose ($$C_6H_{12}O_6$)? Use Avogadro’s number: 6.02$$ \times $$10^{23}$$ molecules/mol.

$$1.51 \times 10$$^{24}$$ molecules

Q: Which of the following is a correct conversion factor for calculating the number of atoms in a sample?

$$\frac{6.02 \times 10$$^{23}$$\ atoms}{1\ mol}$$

Question 1

Which of the following statements best describes Avogadro’s number?

Accepted Answer

It is the number of atoms, molecules, or ions in one mole of a substance.

Question 2

How many molecules are present in 2.50 moles of glucose ($$C_6H_{12}O_6$)? Use Avogadro’s number: 6.02$$ 	imes $$10^{23}$$ molecules/mol.

Accepted Answer

$$1.51 	imes 10$$^{24}$$ molecules

Question 3

What is the molar mass of potassium bromate ($$KBrO_4$$)? (Atomic masses: K = 39.10, Br = 79.90, O = 16.00)

Accepted Answer

$$167.00\ g/mol$$

Question 4

A sample contains $$3.01 	imes 10$$^{23}$$ atoms of sodium. How many moles of sodium are present?

Accepted Answer

$$0.500$$ mol

Question 5

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

It decreases the activation energy, increasing the reaction rate.

Question 6

Which of the following equations is balanced?

Accepted Answer

$$2H_2 + O_2$ \rightarrow 2H_2O$$

Question 7

Which of the following is true for an exothermic reaction?

Accepted Answer

The reaction releases heat to the surroundings.

Question 8

How many grams of $$KI$$ are present in $$0.450$$ moles? (K = 39.10, I = 126.90)

Accepted Answer

$$74.40\ g$$

Question 9

Which of the following best describes oxidation in a redox reaction?

Accepted Answer

Loss of electrons

Question 10

If $$23.5\ g of $$allyl sulfide ($$C_3H_5)_2S) is $$used, how many moles are present? (C = 12.01, H = 1.01, S = 32.07)

Accepted Answer

$$0.250$$ mol

Question 11

Which of the following changes will increase the rate of a chemical reaction?

Accepted Answer

Adding a catalyst

Question 12

In the reaction $$C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(g)$$, how many moles of $$CO_2$$ are produced from 2 moles of $$C_3H_8$$?

Accepted Answer

6 moles

Question 13

Which of the following best describes the transition state in a chemical reaction?

Accepted Answer

The highest energy point along the reaction path

Question 14

Which of the following is a correct conversion factor for calculating the number of atoms in a sample?

Accepted Answer

$$\frac{6.02 	imes 10$$^{23}$$\ atoms}{1\ mol}$$

Question 15

Which of the following is true for an endothermic reaction?

Accepted Answer

The reaction absorbs heat from the surroundings.

Question 16

In the reaction $$(NH_4$)_2SO_4(aq) + Pb(NO_3$)_2(aq) \rightarrow 2NH_4NO_3(aq) + $$PbSO_4$$(s)$$, how many moles of $$NH_4NO_3$$ are produced from 1 mole of $$(NH_4$)_2SO_4$$?

Accepted Answer

2 moles

Question 17

Which of the following best explains why increasing the concentration of reactants increases the rate of reaction?

Accepted Answer

It increases the number of effective collisions per unit time.

Question 18

Which of the following is the correct balanced equation for the combustion of propane ($$C_3H_8$$)?

Accepted Answer

$$C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O$$

Question 19

Which of the following is NOT a requirement for a chemical reaction to occur according to collision theory?

Accepted Answer

Reactants must be in the solid state.

Chemical Quantities and Reactions: Study Guide for GOB Chemistry

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