Answer to Question #331869 in General Chemistry for IAO

Question

A sample of 0.892 g of potassium chloride (KCl) is dissolved in 54.6 g of water (H2O). Determine the percent mass of KCl in the solution and its molality if the molar mass of KCl is 74.5513 grams per mole.

A sample of 0.892 g of potassium chloride (KCl) is dissolved in 54.6 g of water. What is the percent by mass of KCl in the solution?

A sample of 0.892 g of potassium chloride (KCl) is dissolved in 54.6 g of water. What is the percent by mass of KCl in the solution?

The density of a 2.45 M aqueous solution of methanol (CH3OH) is 0.976 g/mL. What is the molality of the solution? The molar mass of methanol is 32.04g.

Answer 1

$W(KCl)=m(KCl)/(m(KCl)+m(H_2O))=0.892/(0.892+54.6)=0.016$

n(KCl)=0.892/74.5513=0.012 mol

$c(KCl)=n(KCl)/m(H_2O)=0.012/0.0546=0.2191mol/kg$

2.

mass of 1l of solution is 976 g=0.976 kg. It contains 2.45 mol of methanol.

Mass of methanol is 976-32.04x 2.45=897.5 g=0.897 kg of water

So c=2.45/0.897=2.73 mol/kg