Question

1)

Syrup used in hummingbird feeders is ofter 25% sucrose (C₁₂H₂₂O₁₁) by mass. If you wish prepare 750 grams of this solution what mass of sucrose (g) and what mass of water (g) would you use?

2)

What is the molality (m) of the solution above? Please give answer to two (2) decimal places

3)

The density of a 25% sucrose solution is 1.10 g/mL. Please calculate the Molarity of this solution.  

Answer 1

Question 1

Given

Mass %of the solution=25%

Mass of the solution=750 g

The formula for mass % is =mass of solute ×100/mass of solution

Or

Mass of solute =mass% ×mass of solution/100

Thus mass of sucrose=25×750g/100

Mass of sucrose=18750g/100

Mass of sucrose=187.50g

Hence the mass of surrose =187.50g

Mass of sucrose+mass of water =mass of solution

Mass of water =mass of solution- mass of sucrose

Mass of water =750g-187.50g

Mass of water=562.50g

Question 2

Molar mass of sucrose=342.3g/mol

Mass of sucrose=187.50g

Moles of sucrose=mass of sucrose/molar mass of sucrose

Moles of sucrose=187.50g/342.3g/mol

Molea of sucrose=0.548moles

Mass of solvent water=562.50g×1Kg/1000g

Mass of solvent=0.5625Kg

Molality=moles of solute/mass of solvent in Kg

Molality=0.548moles/0.5625Kg

Molality=0.974 mol/kg

Question 3

Given

Density of solution=1.10g/ml

Mass of solution=750g

Volume of solution=mass/density

Volume of solution=750g/1.10g/ml

Volume of solution=681.82 ml

Volume of solution=681.82ml×1L/1000ml

Volume of solution 0.68182L

Molarity=moles of solute/vilume of solution in L

Molarity=0.548moles/0.68182L

Molarity=0.804mol/L