Question

A 20.0-9 sample of HF is dissolved in water to give 2.0x 102 mL of solution. The concentration of the solution isa) 1.0 M b) 3.0 M c) 0.10 M d) 5.0 M e) 10. M

Answer 1

D - 5.0 M

Step-by-step explanation

Given

mass of HF = 20.0 g

Volume of the solution = 2.0x10^2 mL

Required: The concentration of HF

Solution

Step 1: Change the volume from mL to L

1 mL = 0.001 L

Therefore volume = 0.2 L

Step 2: Calculate the number of moles of HF

n = m/M where n is the moles, m is the mass and M is the molar mass

n = 20.0g/20,01 g/mol

n = 0.995 mol

Step 3: Calculate the concentration

C = n/V where C is the concentration, n is the moles and V is the volume

C = 0.995 mol/0.2 L

C = 4.9 mol/L = 5.0 M