Q: What is the percent by mass of NaCl in a solution made by dissolving 0.5 g of NaCl in 55.2 g of water?

$$\frac{0.5}{0.5 + 55.2} \times 100 = 0.90\%$$

Q: How many grams of NaCl are needed to prepare 50 mL of a 0.47 m (molal) solution? (Molar mass of NaCl = 58.44 g/mol)

$$0.47 \text{ mol/kg} \times 0.050 \text{ kg} \times 58.44 \text{ g/mol} = 1.37 \text{ g}$$

Q: You have a 5.0 M NaCl stock solution. How much of this stock solution is needed to prepare 250 mL of a 0.15 M NaCl solution?

$$V_1$$ = \frac{$$M_2$$ $$V_2$$}{$$M_1$$} = \frac{0.15 \times 250}{5.0} = 7.5 \text{ mL}$$

Q: What is the molality of a solution containing 25 g of NaCl in 200 mL of H$$_2O$$? (Molar mass NaCl = 58.44 g/mol; density of water = 1.00 g/mL)

$$\text{molality} = \frac{\text{moles of solute}}{\text{kg of solvent}} = \frac{25/58.44}{0.200} = 2.14 \text{ m}$$

Question 1

What is the percent by mass of NaCl in a solution made by dissolving 0.5 g of NaCl in 55.2 g of water?

Accepted Answer

$$\frac{0.5}{0.5 + 55.2} 	imes 100 = 0.90\%$$

Question 2

Which of the following best describes a strong electrolyte?

Accepted Answer

A solute that is completely dissociated into ions in water

Question 3

How many grams of NaCl are needed to prepare 50 mL of a 0.47 m (molal) solution? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

$$0.47 	ext{ mol/kg} 	imes 0.050 	ext{ kg} 	imes 58.44 	ext{ g/mol} = 1.37 	ext{ g}$$

Question 4

Which equation correctly represents the dilution of a solution?

Accepted Answer

$$M_1$$ $$V_1$$ = $$M_2$$ $$V_2$$

Question 5

You have a 5.0 M NaCl stock solution. How much of this stock solution is needed to prepare 250 mL of a 0.15 M NaCl solution?

Accepted Answer

$$V_1$$ = \frac{$$M_2$$ $$V_2$$}{$$M_1$$} = \frac{0.15 	imes 250}{5.0} = 7.5 	ext{ mL}$$

Question 6

Which of the following is a driving force for a double displacement reaction?

Accepted Answer

Formation of a precipitate from soluble reactants

Question 7

A neutralization reaction occurs between which types of substances?

Accepted Answer

An acid and a base

Question 8

Which of the following is true about the total number of moles of solute during dilution?

Accepted Answer

It remains the same

Question 9

Which of the following is NOT a strong electrolyte?

Accepted Answer

Glucose (C$$_6H$_{12}O$_6)$$

Question 10

What is the molality of a solution containing 25 g of NaCl in 200 mL of H$$_2O$$? (Molar mass NaCl = 58.44 g/mol; density of water = 1.00 g/mL)

Accepted Answer

$$	ext{molality} = \frac{	ext{moles of solute}}{	ext{kg of solvent}} = \frac{25/58.44}{0.200} = 2.14 	ext{ m}$$

Question 11

Which of the following best describes a non-electrolyte?

Accepted Answer

A species that does not conduct electricity by the movement of ions

Question 12

In a single displacement reaction, which of the following is true?

Accepted Answer

A more reactive element replaces a less reactive element in a compound

Question 13

Which of the following is the correct definition of solubility?

Accepted Answer

The maximum amount of solute that can be dissolved in a given amount and type of solvent at a fixed temperature

Question 14

Which of the following reactions is a double displacement reaction?

Accepted Answer

$$AB + CD \rightarrow AD + CB$$

Question 15

Which of the following best explains the meaning of the double arrow ($$\rightleftharpoons) in a $$chemical equation?

Accepted Answer

It indicates a state of equilibrium where the forward and reverse reactions occur at the same rate

Question 16

Which of the following is a real-life example of a neutralization reaction?

Accepted Answer

Taking an antacid to relieve heartburn

Question 17

Which of the following statements about weak electrolytes is correct?

Accepted Answer

They partially dissociate in solution

Question 18

A solution is prepared by dissolving 10 g of KNO$$_3 in 100 g of $$water. What is the mole fraction of KNO$$_3$$? (Molar mass KNO$$_3 = 101.1 g/$$mol; Molar mass H$$_2O = 18.02 g/$$mol)

Accepted Answer

$$	ext{Mole fraction} = \frac{0.099}{0.099 + 5.55} = 0.018$$

Question 19

Which of the following best describes a salt formed in a neutralization reaction?

Accepted Answer

An ionic species containing a cation other than hydrogen and an anion other than OH$$^- or O$^{2-}$$

Lecture 24

Guida di studio - Domande di pratica

Study guide - Flashcard