Solutions Topic in Chemistry

Question

1. What mass of solute is required to make a standard solution of K2SO4 with a concentration of

0.65M and a volume of 0.895L?

2. 25.0 mL of 0.350 M NaOH are added to 45.0 mL of 0.125 M copper (II) sulfate. 

a. Write the balanced chemical equation.

b. How many grams of copper (II) hydroxide will precipitate?

3. Mrs.Williams sends you to the chemical store room for a stock solution of 12 mol/L H 2 SO 4 (aq). He

asks you to make 1.5 L of a dilute solution with a concentration of 0.350 mol/L. What volume of

the 12 M acid do you need to use?

Answer 1

1).Molarity=moles/Liter. So 0.65M=moles/.895L,(M)(Volume)=moles, so number of moles=0.582. Multiply by molar mass of K₂SO₄ (174.2g/mole), and obtain 101.34 grams K₂SO_4.

2).2 NaOH + CuSO₄ ---> Cu(OH)₂ + Na₂SO_4.. We make 1 mole of copper hydroxide for every 2 moles of sodium hydroxide and 1 mole of copper(II) sulfate. We have 0.00875 moles of NaOH (Molarity)(Volume) and 0.0056 moles of copper (II) sulfate. The limiting reagent is the NaOH; we will make 0.0.0044 moles of precipitate Multiply by the molar mass of copper hydroxide (114.55 grams/mole) and you obtain 0.5011 grms.

3). M₁V₁=M₂V₂. this is the dilution equation where M stands for molarity ans V stands for volume. So (12M)(V)=(0.350M)(1.5L), solve for V, 43.75 mL.