Q: How many molecules are present in 2.00 moles of water ($$H_2O$$)? Use Avogadro’s number: $$6.022 \times 10$$^{23}$$ molecules/mol.

$$1.20 \times 10$$^{24}$$ molecules

Q: Which of the following conversion factors would you use to convert from moles to particles?

$$\frac{6.022 \times 10$$^{23}$$ \text{ particles}}{1 \text{ mole}}$$

Q: A solution is labeled as $$0.500 M $$NaCl. Which of the following expressions is equivalent to this concentration?

$$\frac{0.500 \text{ mol NaCl}}{1 \text{ L solution}}$$

Q: Which of the following expressions is equivalent to a $$5.45\% (m/v) $$glucose solution?

$$\frac{5.45 \text{ g glucose}}{100 \text{ mL solution}}$$

Q: If you have 93.2 g of $$PH_3 ($$molar mass = 33.99 g/mol), how many molecules of $$PH_3 do $$you have?

$$1.65 \times 10$$^{24}$$ molecules

Question 1

Which of the following best describes the meaning of molar mass?

Accepted Answer

The mass of 1 mole of a substance, which is equal to the molecular (formula) weight of the substance in grams.

Question 2

How many molecules are present in 2.00 moles of water ($$H_2O$$)? Use Avogadro’s number: $$6.022 	imes 10$$^{23}$$ molecules/mol.

Accepted Answer

$$1.20 	imes 10$$^{24}$$ molecules

Question 3

What is the molar mass of $$C_9H_{16}ClNO$$ based on the atomic weights: C = 12.011, H = 1.00794, Cl = 35.4527, N = 14.0067, O = 15.9994?

Accepted Answer

$$201.70$$ amu

Question 4

Which of the following conversion factors would you use to convert from moles to particles?

Accepted Answer

$$\frac{6.022 	imes 10$$^{23}$$ 	ext{ particles}}{1 	ext{ mole}}$$

Question 5

A solution is labeled as $$0.500 M $$NaCl. Which of the following expressions is equivalent to this concentration?

Accepted Answer

$$\frac{0.500 	ext{ mol NaCl}}{1 	ext{ L solution}}$$

Question 6

Which of the following expressions is equivalent to a $$5.45\% (m/v) $$glucose solution?

Accepted Answer

$$\frac{5.45 	ext{ g glucose}}{100 	ext{ mL solution}}$$

Question 7

If you have 93.2 g of $$PH_3 ($$molar mass = 33.99 g/mol), how many molecules of $$PH_3 do $$you have?

Accepted Answer

$$1.65 	imes 10$$^{24}$$ molecules

Question 8

A reaction has a rate law: $$	ext{rate} = k[A]^3[B]^2. If $$the concentrations of both A and B are doubled, by what factor does the rate increase?

Accepted Answer

32

Question 9

Which statement best describes an endothermic reaction?

Accepted Answer

A reaction that absorbs heat from the surroundings.

Question 10

According to Le Châtelier’s principle, what will happen if more reactant is added to a system at equilibrium?

Accepted Answer

The equilibrium will shift to produce more products.

Question 11

In a chemical reaction, the limiting reactant is:

Accepted Answer

The reactant that is completely consumed first, limiting the amount of product formed.

Question 12

If 37.4 g of $$O_2$$ would produce 42.1 g of $$H_2O$$, and 44.7 g of $$H_2S$$ would produce 23.6 g of $$H_2O$$, but only 15.8 g of $$H_2O is $$actually formed, what is the percent yield?

Accepted Answer

$$66.9\%$$

Question 13

What is the mass of KBr present in a $$0.959\,m$$ KBr solution if there are $$0.350 kg of $$solvent? (K = 39.10, Br = 79.90)

Accepted Answer

$$39.9 g$$

Question 14

What volume of $$4.00 M $$HCl should be diluted to prepare $$75.00 mL of a$$ $$1.25 M $$HNO$$_3$$ solution?

Accepted Answer

$$23.4 mL$$

Question 15

Which of the following best describes the law of conservation of energy?

Accepted Answer

Energy can be neither created nor destroyed in any physical or chemical change.

Question 16

A positive entropy change ($$\Delta S) $$for a process means:

Accepted Answer

Disorder increases in the system.

Question 17

A reaction is said to be exergonic if:

Accepted Answer

Free energy is released and the reaction is spontaneous.

Question 18

What volume of methanol is present in $$35.0 mL of an$$ $$8.22\% (v/v) $$ethanol solution?

Accepted Answer

$$2.88 mL$$

Mass and Mole Relationships, Energy, and Solution Calculations in GOB Chemistry

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