Retest: Stoichiometry 4/15

Which sample represents a homogeneous mixture?

• CO₂(s)

• CO₂(s)

• CO₂(aq)

• CO₂(g)

Answer explanation

The correct choice is CO₂(aq) because it represents carbon dioxide dissolved in water, which is a homogeneous mixture where the components are uniformly distributed.

The molarity (M) of a solution is equal to the

• number of grams of solute per liter of solvent

• number of moles of solute per liter of solution

• number of grams of solute per liter of solution

• number of moles of solute per liter of solvent

Answer explanation

The molarity of a solution is defined as the number of moles of solute per liter of solution, making it the correct choice.

A 1,000. gram sample of drinking water was found to contain 2.5 x 10⁻³ grams chlorine. What is the concentration of chlorine in parts per million (ppm)?

• 2.5 ppm

• 2.5 x 10¹¹ ppm

• 2,500 ppm

• 2.5 x 10⁶ ppm

Answer explanation

To convert grams to parts per million (ppm), we use the formula: (mass of solute / mass of solution) x 10^6. Plugging in the values, we get (2.5 / 1000) x 10^6 = 2.5 ppm.

Which solution has the highest boiling point?

• 1 mole of NaNO₃ in 1,000 g of water

• 1 mole of NaNO₃ in 750 g of water

• 1 mole of NaNO₃ in 500 g of water

• 1 mole of NaNO₃ in 250 g of water

Answer explanation

The solution with the highest boiling point is 1 mole of NaNO₃ in 250 g of water, as the concentration of the solute is highest in this case, leading to stronger intermolecular forces and a higher boiling point.

Solutions of AgNO₃(aq) and KCl(aq) are mixed. Will a visible reaction occur?

• Yes, because KNO₃ will precipitate out of solution.

• No, because AgCl is soluble in water.

• No, because KNO₃ is soluble in water.

• Yes, because AgCl will precipitate out of solution.

Answer explanation

The correct choice is 'Yes, because AgCl will precipitate out of solution.' as a visible reaction will occur due to the formation of a precipitate.

Based on the given table, which saturated solution would be the least concentrated?

• barium sulfate

• sodium sulfate

• lithium sulfate

• potassium sulfate

Answer explanation

The least concentrated saturated solution would be lithium sulfate based on the given table.

Which solution will freeze at the lowest temperature?

• 2 moles of sugar in 1,000 g of water

• 1 mole of sugar in 500 g of water

• 2 moles of sugar in 500 g of water

• 1 mole of sugar in 1,000 g of water

Answer explanation

The solution with 2 moles of sugar in 500 g of water will freeze at the lowest temperature due to the higher concentration of solute particles.

According to the given table, what is the maximum number of grams of NH4Cl that will dissolve in 200 grams of water at 70°C?

• 100 g

• 124 g

• 85 g

• 62 g

Answer explanation

The maximum solubility of NH4Cl in water at 70°C is 124 g, as shown in the table. Therefore, 124 g is the correct choice for the maximum grams of NH4Cl that will dissolve in 200 grams of water at 70°C.

A solution containing 55 grams of NH₄Cl in 100 grams of water is saturated at a temperature of

• 67°C

• 57°C

• 77°C

• 47°C

Answer explanation

The correct temperature for the solution to be saturated is 57°C, as this is the temperature at which NH4Cl solubility in water is 55 grams in 100 grams of water.

A solution of KCl(aq) contains 15 grams of solute in 85 grams of water. What is the concentration of the solution in percent by mass?

• 0.20%

• 15%

• 2.0%

• 6.0%

Answer explanation

The concentration of the solution is calculated by dividing the mass of solute by the total mass of the solution and multiplying by 100. In this case, (15g / 100g) * 100 = 15%. Therefore, the concentration of the solution is 2.0%.