Question

add 150 mL of h20 to 100 mL 0.250 M HCl. What will be the molarity of the solution?

Can you use the formula M1V1=M2V2 in this problem?

Answer 1

Calculation by method I

moles of HCl intially in solution = M x L = 0.250 M x 0.100 L = 0.025 moles

total new volume of solution = 150 ml + 100 ml = 250 ml = 0.250 L

So, molarity of HCl in total volume of solution = moles of HCl / total new volume of solution

                                                                         = 0.025/0.250 = 0.1 M

calculation by method II

using, M1V1 = M2V2

where,

M1 = 0.250 M

V1 = 100 mL

M2 = unknown

V2 = 100+150 = 250 ml

Feed values,

0.250 M x 100 ml = 250 ml x M2

M2 = 0.1

thus, the molarity of solution now would be 0.1 M and we can use M1V1 = M2V2 to calculate the new molarity of solution.