Solutions - Calculations

A 0.20 mol sample of MgCl_2(s) and a 0.10 mol sample of KCl_(s) are dissolved in water and diluted to 500 mL. What is the concentration of Cl^- in the solution?

• 0.15 M

• 0.30 M

• 0.50 M

• 0.60 M

• 1.0 M

A 360. mg sample of aspirin, C₉H₈O₄, (molar mass 180. g), is dissolved in enough water to produce 200. mL of solution. What is the molarity of aspirin in a 50. mL sample of this solution?

• 0.0800 M

• 0.0400 M

• 0.0200 M

• 0.0100 M

• 0.00250 M

A 40.0 mL sample of 0.25 M KOH is added to 60.0 mL of 0.15 M Ba(OH)₂. What is the molar concentration of OH^-_(aq) in the resulting solution? (Assume that the volumes are additive.)

• 0.10 M

• 0.19 M

• 0.28 M

• 0.40 M

• 0.55 M

A student prepares a solution by dissolving 60.00 g of glucose (molar mass 180.2 g mol^-1) in enough distilled water to make 250.0 mL of solution. The molarity of the solution should be reported as

• 12.01 M

• 12.0 M

• 1.332 M

• 1.33 M

• 1.3 M

A student wishes to prepare 2.00 liters of 0.100–molar KIO₃ (molecular weight 214). The proper procedure is to weigh out

• 42.8 grams of KIO₃ and add 2.00 kilograms of H₂O

• 42.8 grams of KIO₃ and add H₂O until the final homogeneous solution has a volume of 2.00 liters

• 21.4 grams of KIO₃ and add H₂O until the final homogeneous solution has a volume of 2.00 liters

• 42.8 grams of KIO₃ and add 2.00 liters of H₂O

• 21.4 grams of KIO₃ and add 2.00 liters of H₂O

Approximately what mass of CuSO₄ • 5H₂O (250 g mol^-1) is required to prepare 250 mL of 0.10 M copper(II) sulfate solution?

• 4.0 g

• 6.2 g

• 34 g

• 85 g

• 140 g

Fe³⁺_(aq) + KSCN_(s) → FeSCN²⁺_(aq) + K⁺_(aq)

To determine the moles of Fe³⁺_(aq) in a 100. mL sample of an unknown solution, excess KSCN_(s) is added to convert all the Fe³⁺_(aq) into the dark red species FeSCN²⁺_(aq), as represented by the equation above. The absorbance of FeSCN²⁺_(aq) at different concentrations is shown in the graph above.

If the absorbance of the mixture is 0.20 at 453 nm, how many moles of Fe³⁺_(aq) were present in the 100. mL sample? (Assume that any volume change due to adding the KSCN_(s) is negligible.)

• 4 × 10⁻⁴ mol

• 3 × 10⁻⁴ mol

• 4 × 10⁻⁶ mol

• 3 × 10⁻⁶ mol

For an experiment, a student needs 100.0 mL of 0.4220 M NaCl. If the student starts with NaCl_(s) and distilled water, which of the following pieces of laboratory glassware should the student use to prepare the solution with the greatest accuracy?

• 25 mL volumetric pipet

• 100 mL Erlenmeyer flask

• 100 mL graduated cylinder

• 100 mL volumetric flask

• 1 L beaker

How many mL of 10.0 M HCl are needed to prepare 500. mL of 2.00 M HCl ?

• 1.00 mL

• 10.0 mL

• 20.0 mL

• 100. mL

• 200. mL

If 200. mL of 0.60 M MgCl_2(aq) is added to 400. mL of distilled water, what is the concentration of Mg²⁺_(aq) in the resulting solution? (Assume volumes are additive).

• 0.20 M

• 0.30 M

• 0.40 M

• 0.60 M

• 1.2 M