Question

Which solutions have a concentratoin of 1.0 M?
i. 74 grams of calcium hydroxide dissolved to make 1 liter of solution
ii. 74.5 grams of potassium chloride dissolved to maek 1 liter of solution
iii. 87 grams of lithium bromide dissolved to make 1 liter of solution

• A. i only
• B. iii only
• C. i and iii only
• D. ii and iii only
• E. i, ii and iii

Answer 1

The correct option is E i, ii and iii

All three solutions have a concentratoin of 1.0 M.
i. 74 grams of calcium hydroxide dissolved to make 1 liter of solution
The molar mass of calcium hydroxide is 74 g/mol. Hence, 74 grams of calcium hydroxide corresponds to 1 mole. When 1 mole of solute is dissolved in 1 L of solution, the concentration is 1 M.
Concentration $=\frac{74g}{74g/mol\times 1L}=1$ M
ii. 74.5 grams of potassium chloride dissolved to make 1 liter of solution
The molar mass of potassium chloride is 74.5 g/mol. Hence, 74.5 grams of potassium chloride corresponds to 1 mole. When 1 mole of solute is dissolved in 1 L of solution, the concentration is 1 M.
Concentration $=\frac{74.5g}{74.5g/mol\times 1L}=1$ M
iii. 87 grams of lithium bromide dissolved to make 1 liter of solution
The molar mass of lithium bromide is 87 g/mol. Hence, 87 grams of calcium hydroxide corresponds to 1 mole. When 1 mole of solute is dissolved in 1 L of solution, the concentration is 1 M.
Concentration $=\frac{87g}{87g/mol\times 1L}=1$ M