Question

A stock bottle of an acid reads: 56% by mass and 1.25 specific gravity. If the molar mass of the acid is 70g, find the mole per cubic decimeter

Answer 1

To find the mole per cubic decimeter of an acid given the mass percentage and specific gravity, calculate the mass of the acid in one cubic decimeter of the solution, convert the mass to moles, and then divide the number of moles by the volume in cubic decimeters.

Step-by-step explanation:

The question asks to find the mole per cubic decimeter of an acid given the mass percentage and specific gravity. To solve this, we first need to calculate the mass of the acid in one cubic decimeter of the solution. Since we know the molar mass of the acid is 70g, we can find the number of moles by dividing the mass by the molar mass. Finally, we divide the number of moles by the volume in cubic decimeters to find the mole per cubic decimeter.

Answer 2

• 10 mol / dm³

Step-by-step explanation:

Cubic decimeter is the same unit as liter; so, mole per cubic decimeter is mole per liter, and that is the unit of concentration of molarity. Thus, what is asked is the molarity of the solution. This is how you find it.

1. Take a basis: 1 dm³ = 1 liter = 1,000 ml

2. Calculate the mass of 1 liter (1,000 ml) of solution:

• density = mass / volume ⇒ mass = density × volume

Here, the density is given through the specific gravity

Scpecific gravity = density of acid / density of water

Take density of water as 1.00 g/ml.

• density of solution = 1.25 g/ml

• mass solution = 1.25 g/ml × 1,000 ml = 1,250 g

3. Calculate the mass of solute (pure acid)

• % m/m = (mass of solute / mass of solution) × 100

• 56 = mass of solute / 1,250 g × 100

• mass of solute = 56 × 1,250g / 100 = 700 g

4. Calculate the number of moles of solute:

• moles = mass in grams / molar mass = 700 g / 70 g/mol = 10 mol

5. Calculate molarity (mol / dm³)

• M = number of moles of solute / liter of solution = 10 mol / 1 liter = 10 mol/liter.