Answer to Question #254846 in General Chemistry for MATO

Question

Calculate the volume of acid needed to prepare 500ml of 2.0 molar concentration of acid,if the stock bottle of the acid reads 1.25 specific gravity, 56% by mass and molar mass of acid 56.

Answer 1

To calculate the molarity of a solution that is 56% by mass, begin by calculating the total mass of one L of the solution. Given that the specific gravity of the solution is 1.25, we know that one L of the solution weighs 1250g. Multiplying the total weight by the percentage we get the number of grams of acid per liter.

$56.0 \% \times 1250 \;g/L = 700 \;g/L$

Then divide by the molecular weight to obtain the molarity.

$Molarity = 700 \;g/L \times \frac{1\;mol}{56 \;g} = 12.5 \;M$

500 ml of 2.0 M solution will contain 1 mol of acid.

Proportion:

12.5 mol – 1000 mL

1 mol – x

$x = \frac{1 \times 1000}{12.5} = 80 \;mL$

Answer: 80 mL