Answer:
33.8 m
Explanation:
(a) We want to know the molality of nitric acid in a concentrated solution of nitric acid (68.0% HNO₃ by mass).
Step 1: Determine the mass of HNO₃ and water in 100 grams of solution.
Step 2: Convert the mass of HNO₃ to moles.
Step 3: Convert the mass of water to kilograms.
Step 4: Calculate the molality.
(b)
Step 1
In 100 g of solution, there are 68.0 g of HNO₃ and 100 g - 68.0 g = 32.0 g of water.
Step 2
The molar mass of HNO₃ is 63.01 g/mol. The moles corresponding to 68.0 g are:
68.0 g × (1 mol/63.01 g) = 1.08 mol
Step 3
The mass of water is 32.0 g = 0.0320 kg
Step 4
The molality of HNO₃ is:
m = moles of solute / kilograms of solvent
m = 1.08 mol / 0.0320 kg
m = 33.8 m
Answer:
The molality of HNO3 is 33.75 molal
Explanation:
Step 1: Data given
mass % of HNO3 = 68 %
Step 2: Calculate masses
If the mass % of HNO3 is 68 %, this means that 68 of 100 grams are HNO3
This means that 100-68 = 32 grams are water.
So mass HNO3 = 68 grams
Mass H2O = 32 grams
mass solution = 100 grams
Step 3: Calculate moles HNO3
Moles HNO3 = mass HNO3 / molar mass HNO3
Moles HNO3 = 68.0 grams / 63.02 g/mol
Moles HNO3 = 1.08 moles
Step 4: Calculate molality
Molality = number of moles HNO3 / mass of water
Molality = 1.08 moles / 0.0320 kg
Molality = 33.75 molal
The molality of HNO3 is 33.75 molal
