26 5.3 Concentration and Solutions

Figures

Figure 5.3.3

A 3D molecular model displaying a salt crystal lattice interspersed with water and potassium molecules, as an illustration of potassium chloride dissolving into water. There are spheres labeled K⁺, representing potassium ions, and other spheres labeled Cl^–, representing chloride ions, arranged in an alternating cubic pattern. Surrounding this ionic lattice are several water molecules, and the orientation of the water molecules suggests hydration shells, where the oxygen atoms are attracted to the potassium ions and the hydrogen atoms are oriented towards the chloride ions, highlighting the ionic dissolution process in water.

Practice questions

Multiple choice questions

1. A sodium chloride solution contains 3.56g of sodium chloride dissolved in a final volume of 25.0 mL. What is the percent concentration of sodium chloride in m/v?
   1. 14.2%m/v
   2. 7.02%m/v
   3. 89%m/v
   4. 85.5%m/v
2. When 2.50g of LiBr is dissolved in 25.0g of water, it gives a 10.0%m/m LiBr solution. Calculate the mass of LiBr present in 15.0g of the same solution.
   1. 0.150g
   2. 1.50g
   3. 1g
   4. 10g
3. A diluted NaOH solution was prepared by adding 100.0mL of water to the 400.0mL of the 0.1M stock solution. What is the molarity of the diluted NaOH solution?
   1. 0.08M
   2. 25M
   3. 0.04M
   4. 12.5M
4. 50.0mL of a NaOH stock solution with a concentration of 10.0%m/v is diluted to 250.0mL. What is the final concentration of the NaOH solution in m/v %?
   1. 5.00%m/v
   2. 0.02%m/v
   3. 2.00%m/v
   4. 20%m/v

Short-answer questions

1. Calculate the molarity of the following solutions, then put the correct answer into the boxes. Round the answers to 2 d.p. if needed.
   • 3.0mol of Silver nitrate in 0.50L of solution- _________ M
   • 0.0625mol of Sodium bicarbonate in 250.0mL of solution- _________M
2. Calculate the mass in grams of the solute in each of the following solutions, then put the correct answer into the spaces. Round the answers to 2 d.p. if needed.
   • 750.0mL of a 1.50M NaOH solution- _________ g
   • 0.200L of a 150.0mM NaCl solution- __________ g

   Note: The molar masses of NaOH and NaCl are 39.997g/mol and 58.44g/mol, respectively.

3. Calculate the molarity of a 5.0%m/v KOH solution, then put the correct answer into the space.
   Note: the molar mass of KOH is 56.1056g/mol. Round the answers to 2 d.p. if needed.
   The Molarity of a 5.0% m/v KOH solution= _________ M

Solutions

Multiple choice questions

1. a
2. b
3. a
4. c

Short-answer questions

1. 6; 0.25
2. 45; 1.75
3. 0.89