Organic Chemistry Density

Question

If an experiment asks you to use 16.5 mmol of an organic liquid that has a molecular weight of 163.52 g/mol and a density of 0.946 g/mL, what volume (in mL) should be measured out? Give your answer to 1 decimal place only.

Answer 1

QUESTION

If an experiment asks you to use 16.5 mmol of an organic liquid that has a molecular weight of 163.52 g/mol and a density of 0.946 g/mL, what volume (in mL) should be measured out? Give your answer to 1 decimal place only.

SOLUTION

GIVEN DATA:

Mol = 16.5 mmol = 16.5 x 10^-3 mol

Molecular mass = Molar mass = 163.52 g/mol

Density = d = 0.946 g/mL

Mol = mass (g) / molar mass (g/mol)

Mass (g) = Mol x Molar mass (g/mol)

Mass (g) = 16.5 x 10^-3 mol x 163.52 g/mol = 2.7 g

Density = mass (g) / volume (mL)

D = m / v

Volume = v = m / d = 2.7 g / 0.946 g/mL= 2.85 mL = 2.9 mL

ANSWER

Volume (v) = 2.9 mL

Answer 2

It's a dimensional analysis problem.

16.5 mmol × 10^–3 mol/mmol = 1.65 × 10^–2 mol

1.65 × 10^–2 mol × 163.52 g/mol = 2.698 g

2.698 g × 1mL/0.946 g = 2.85 mL

In each step you multiply by a conversion factor that has

1. the units you are converting to in the numerator, and
2. the units you are converting from in the denominator

After cancellation, your units get converted to the units of the numerator.

Answer (to one decimal place)

2.9 mL