1) You want to make 650 mL of 0.150 M potassium hydrogen phosphate.

How many moles of potassium hydrogen phosphate do you need?

2) You have in stock a solution that is 0.800M potassium hydrogen phosphate.

How much of this solution would you use to make your solution?

3) How can you check the molarity of your final potassium hydrogen phosphate solution?

Question

1) You want to make 650 mL of 0.150 M potassium hydrogen phosphate.

How many moles of potassium hydrogen phosphate do you need?

2) You have in stock a solution that is 0.800M potassium hydrogen phosphate.

How much of this solution would you use to make your solution?

3) How can you check the molarity of your final potassium hydrogen phosphate solution?

| General Chemistry 2

Accepted Answer

Potassium hydrogen phosphate: K₂HPO₄

1) n_K2HPO4 = M_K2HPO4 x V_K2HPO4

n_K2HPO4 = 0.150 x 650 x 10^-3

n_K2HPO4= 9.75 x 10^-2 mol

2) solution 1: 0.800 M potassium hydrogen phosphate

solution 2: 0.150M potassium hydrogen phosphate

During a dilution: conservation of the number of moles

⇒ n₁ = n₂

⇒ M₁x V₁ = M₂ x V₂
⇒ V₁ = $\frac{M_{2} \times V_{2}}{M_{1}}$ = $\frac{0.150 \times 650}{0.800}$ = 1.22 x 10² mL

3) Titration with an acidic solution with a known concentration (for example 1 M HCl solution)

Midterm 1 - Question 1 | General Chemistry 2