Question

What is the molarity and molality of a solution that is 10.00 % by mass potassium hydrogen carbonate (KHCO3, 100.11 g/mol) and has a density of 1.0650 g/mL

Answer 1

Answer: The molarity and molality of a solution is 1.06 M and 1.11 m respectively.

Explanation:

Molality of a solution is defined as the number of moles of solute dissolved per kg of the solvent.

$Molality=\frac{n\times 1000}{W_s}$

where,

n = moles of solute  =

$W_s$ = weight of solvent in g

10.00 g of potassium hydrogen carbonate in 100 g of solution

mass of solvent = mass of solution - mass of solute = (100.0-10.00) = 90.0 g

$Molality=\frac{0.09985\times 1000}{90.0}=1.11m$

2. Molarity of a solution is defined as the number of moles of solute dissolved per Liter of the solution.

$Molarity=\frac{n\times 1000}{V_s}$

where,

n= moles of solute  = 0.09985

$V_s$ = volume of solution in ml

Density of solution = 1036.5 g/L

Volume of solution =$\frac{\text {mass of solution}}{\text {Density of solution}}=\frac{100.0g}{1.0650g/ml}=93.90ml$

$Molality= \frac{0.09985\times 1000}{93.90ml}=1.06M$