U8 Solutions Review

Which barium salt is insoluble in water?

• BaCO₃

• BaCl₂

• Ba(OH)₂

• Ba(NO₃)₂

Answer explanation

BaCO3 (barium carbonate) is insoluble in water, while BaCl2, Ba(OH)2, and Ba(NO3)2 are soluble. Therefore, the correct answer is BaCO3.

According to your Reference Tables, which substance forms an unsaturated solution when 80 grams of the substance is dissolved in 100 grams of H₂O at 10°C?

• KI

• KNO₃

• NaNO₃

• NaCl

Answer explanation

KI forms an unsaturated solution when 80 grams is dissolved in 100 grams of H2O at 10°C, as its solubility exceeds this amount. The other substances would saturate the solution at lower amounts.

The solubility of KClO₃(s) in water increases as the

• temperature of the solution increases

• temperature of the solution decreases

• pressure on the solution increases

• pressure on the solution decreases

Answer explanation

The solubility of KClO3(s) increases with temperature because higher temperatures provide more energy, allowing more KClO3 to dissolve in water. Thus, the correct choice is that the temperature of the solution increases.

The solubility of NH₃ (g) in water increases as the

• temperature of the solution increases and the pressure increases

• temperature of the solution decreases and the pressure increases

• temperature of the solution increases and the pressure decreases

• temperature of the solution decreases and the pressure decreases

Answer explanation

The solubility of NH3 in water increases when the temperature decreases because lower temperatures favor gas solubility. Additionally, increasing pressure enhances solubility by pushing more gas into the solution, making the correct choice: temperature decreases and pressure increases.

Tags

NGSS.HS-PS3-4

A solution contains 35 grams of KNO₃ dissolved in 100 grams of water at 40°C. How much more KNO₃ would have to be added to make it a saturated solution?

• 29 g

• 24 g

• 12 g

• 4 g

Answer explanation

At 40°C, the solubility of KNO3 in water is about 64 g per 100 g of water. Since 35 g is already dissolved, you can add 29 g more to reach saturation (64 g - 35 g = 29 g). Thus, the correct answer is 29 g.

According to Reference Table G, how many grams of KNO₃ would be needed to saturate 200 grams of water at 70°C?

• 43 g

• 86 g

• 134 g

• 268 g

Answer explanation

To saturate 200 grams of water at 70°C, you need 134 grams of KNO3 per 100 grams of water. Therefore, for 200 grams, it would be 134 g x 2 = 268 g, making 268 g the correct answer.

Carbon dioxide gas is most soluble in water under conditions of

• high pressure and low temperature

• high pressure and high temperature

• low pressure and low temperature

• low pressure and high temperature

Answer explanation

Carbon dioxide is more soluble in water at high pressure because increased pressure forces more gas into the liquid. Low temperature also enhances solubility as gases are less likely to escape, making 'high pressure and low temperature' the correct choice.

When PbI₂(s) is added to Na₂CO₃(aq), a white precipitate is formed. According to Reference Table F, the white precipitate most likely is

• KNO₃

• PbCO₃

• NaI

• Na₂CO₃

Answer explanation

When PbI2(s) reacts with Na2CO3(aq), PbCO3 forms as a white precipitate. This is due to the reaction between lead ions and carbonate ions, leading to the formation of insoluble PbCO3, confirming it as the correct choice.

As additional KNO₃(s) is added to an already saturated solution of KNO₃ at constant temperature, the concentration of the solution

• increases with additional solute

• increases with additional solvent

• remains the same with additional solute

• remains the same with additional solvent

Answer explanation

In a saturated solution, the maximum concentration of solute is reached. Adding more KNO3(s) does not increase the concentration, as it cannot dissolve further. Thus, the concentration remains the same with additional solute.

What is the total number of moles of NaCl(s) needed to make 3.0 liters of a 2.0 M NaCl solution?

• 6.0 mol

• 3.0 mol

• 1.0 mol

• 0.70 mol

Answer explanation

To find the total moles of NaCl needed, use the formula: moles = molarity × volume. Here, moles = 2.0 M × 3.0 L = 6.0 mol. Thus, the correct answer is 6.0 mol.