Answer:
a. 74.55 g/mol.
b. 91.70 g.
c. 8.40%.
d. 1.23 mol/L.
Explanation:
<em>a. Calculate the formula weight of KCl.</em>
∵ Formula weight of KCl = atomic weight of K + atomic weight of Cl
atomic weight of K = 39.098 g/mol, atomic weight of Cl = 35.45 g/mol.
∴ Formula weight of KCl = atomic weight of K + atomic weight of Cl = 39.098 g/mol + 35.45 g/mol = 74.548 g/mol ≅ 74.55 g/mol.
<em>b. Calculate the mass of KCl in grams.</em>
<em>no. of moles (n) = mass/molar mass.</em>
∴ mass of KCl = n*molar mass = (1.23 mol)*(74.55 g/mol) = 91.69 g ≅ 91.70 g.
<em>c. Calculate the percent by mass of KCl in this solution.</em>
The mass % of KCl = (mass of KCl/mass of the solution) * 100.
mass of KCl = 91.70 g,
mass of the solution = 1000.0 g of water + 91.70 g of KCl = 1091.70 g.
∴ The mass % of KCl = (91.70 g/1091.70 g)*100 = 8.399% ≅ 8.40%.
<em>d. Calculate the molarity of the solution.</em>
Molarity is the no. of moles of solute per 1.0 L of the solution.
<em>M = (no. of moles of KCl)/(Volume of the solution (L))</em>
no. of moles of KCl = 1.23 mol,
Volume of the solution = mass of water / density of water = (1000.0 g)/(1.00 g/mL) = 1000.0 mL = 1.0 L.
M = (1.23 mol)/(1.0 L) = 1.23 mol/L.
