Solutions: % by Volume & Dilutions

If a solution is made by taking 70. mL of ethanol and adding enough water to make 750 mL of solution, the percent volume is:

• 9.3%

• 10.%

• 0.093%

• 70%

Which formula will you use for a problem looking for concentration by volume of isopropyl alcohol in a solution?

Which describes a solvent? (Choose TWO correct answers)

• The substance that does the dissolving in a solution.
• The substance that is being dissolved in a solution.
• The substance present in smaller amount in a solution

• The substane present in larger amount in a solution

What volume of ethanol is needed to prepare a 25.0 mL aqueous solution that is 15% ethanol by volume?

• 375 ml

• 37.5 ml

• 3.75 ml

• 1.67 ml

• 167 mL

What is the concentration, in percent by volume, of 15.3 mL of solute in 2.65 L of solution?

• 0.58%
• 0.0058%
• 5.8%
• 580%

Answer explanation

Make sure your units are consistent before you start the solution calculation (both values in mL, or both values in L)

When you dilute a solution, which of these values remains constant (the same)?

• The concentration of the solution

• The total amount of solute

• The volume of the solution

• The total amount of solvent

As we dilute a solution...

• The volume increases and the concentration increases

• The volume decreases and the concentration increases

• The volume increases and the concentration decreases

• The volume decreases and the concentrations decreases

50 ml of a 1.0 M stock solution is diluted until the final volume is 80 ml. What is the molarity of the working solution?

• 4000 mL

• 1.6 M

• 130 ml

• 0.63 M

You can make a solution more concentrated by... (Choose TWO correct answers)

• adding more solute

• adding more solvent

• boiling away (or evaporating) some solute

• boiling away (or evaporating) some solvent

How many mL of WATER will you need to add to a 19% M NaCl stock solution to make 100. mL of a 6.0% NaCl solution?

• 32 mL

• 87 mL

• 68 mL

• 320 mL