Calculate the mass of NaCl in a 35-mL sample of a 1.3 M NaCl solution.

Solution: here, we are going to calculate the mass of NaCl in the sample solution.

Step1:

Molarity(M) is defined as number of moles of solute dissolved in one litre (or one cubic decimetre) of solution.

Moles of solute

Molarity = ------------------------------- ------(1)

Volume of solution in litre

Step2:

In the above problem,

Volume of the solution = 35 mL = 35 / 1000 L = 0.035 L [1000 mL = 1 L]

Molarity of the solution = 1.3 M

Substituting the values in equation (1), we get,

1.3 M = moles of NaCl / 0.035 L

Therefore, moles of NaCl = 1.3 M x 0.035 L

= 0.0455 mol

Step3:

1 mol NaCl = molar mass of NaCl

0.0455 mol NaCl = 0.0455 x molar mass of NaCl

= 0.0455 x 58.44 g/mol

= 2.659 g.

Thus, the mass of NaCl is 2.659 g.

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