Solutions and Concentration - SS1 Chemistry Past Questions and Answers - page 3
Which concentration unit is defined as the number of moles of solute per kilogram of solvent?
Molarity
Molality
Mass percentage
Mole fraction
Which concentration unit is expressed as the ratio of the mass of solute to the total mass of the solution, multiplied by 100?
Molarity
Molality
Mass percentage
Mole fraction
Which concentration unit is defined as the ratio of the moles of a component to the total number of moles in the solution?
Molarity
Molality
Mass percentage
Mole fraction
Which concentration unit is temperature-dependent?
Molarity
Molality
Mass percentage
Mole fraction
Which concentration unit is independent of temperature?
Molarity
Molality
Mass percentage
Mole fraction
Which concentration unit is commonly used in colligative property calculations?
Molarity
Molality
Mass percentage
Mole fraction
Which concentration unit is useful for expressing the concentration of solutes in solid-liquid solutions?
Molarity
Molality
Mass percentage
Mole fraction
Which concentration unit is frequently used in gas phase mixtures?
Molarity
Molality
Mass percentage
Mole fraction
Which concentration unit takes into account the solvent's mass rather than its volume?
Molarity
Molality
Mass percentage
Mole fraction
What is the molarity of a solution containing 25 grams of NaCl dissolved in 500 mL of water?
Step 1: Convert the given mass of NaCl to moles.
Molar mass of NaCl = 22.99 g/mol (sodium) + 35.45 g/mol (chlorine) = 58.44 g/mol
Number of moles of NaCl = Mass of NaCl / Molar mass of NaCl
= 25 g / 58.44 g/mol
≈ 0.428 mol
Step 2: Convert the given volume of water to litres.
Volume of water = 500 mL = 500/1000 L = 0.5 L
Step 3: Calculate molarity using the formula:
Molarity (M) = Number of moles of solute / Volume of solution (in litres)
= 0.428 mol / 0.5 L
= 0.856 M
The molarity of the solution is 0.856 M.