Question

How many milliliters of 5.5 M HCl solution are needed to obtain 0.14 mol of HCl?

Express the volume in milliliters to two significant digits

How many moles of KBr are present in 140. mL of a 0.128 M solution?

Express the amount in moles to three significant digits.

Answer 1

Molarity = (no. of moles)/volume of solution(in L)

volume of 5.5 M HCl solution needed to obtain 0.14 mol of HCl is:

5.5 M = 0.14 mol/volume

or, volume of solution = 0.14/5.5 = 0.025 L = 25. mL

Hence, 25. mL of 5.5 M HCl solution is needed to obtain 0.14 mol of HCl.

The number of moles of KBr present in 140. mL of a 0.128 M solution is given by:

0.128 M = (number of moles)/(140 x 10^-3 L)

number of moles = (0.128)x(0.140) = 0.0179 mol

Hence, 0.0179 mol of KBr are present in 140. mL of a 0.128 M solution