Here below some basic MCQ’s about “Concentration Terms” which is explained in details. Let’s check one by one.
1. Which of the following is an example of a concentration term that is independent of temperature?
a) Molarity
b) Molality
c) Normality
d) Volume percent
Answer: b) Molality
Explanation:
Molality is defined as the number of moles of solute per kilogram of solvent. Since it is based on mass (kg) rather than volume, it is independent of temperature. On the other hand, molarity (moles/liter) and normality depend on volume, which can change with temperature.
2. Which of the following concentration terms expresses the number of moles of solute present in one liter of solution?
a) Molality
b) Molarity
c) Normality
d) Mole fraction
Answer: b) Molarity
Explanation:
Molarity (M) is defined as the number of moles of solute divided by the volume of the solution in liters. It is temperature-dependent as it involves volume, which can expand or contract with temperature changes.
3. A solution is prepared by dissolving 10 g of NaCl in 90 g of water. The molality of the solution is closest to:
(Molecular weight of NaCl = 58.5 g/mol)
a) 1.71 mol/kg
b) 1.53 mol/kg
c) 1.90 mol/kg
d) 2.15 mol/kg
Answer: a) 1.71 mol/kg
4. What is the mole fraction of ethanol in a solution containing 46 g of ethanol (C₂H₅OH) and 180 g of water?
(Molecular weight of ethanol = 46 g/mol, water = 18 g/mol)
a) 0.20
b) 0.30
c) 0.40
d) 0.25
Answer: a) 0.20
5. A solution has a molarity of 2 M and density of 1.25 g/mL. What is the molality of the solution if the molar mass of the solute is 58.5 g/mol?
a) 1.9 mol/kg
b) 2.5 mol/kg
c) 3.4 mol/kg
d) 4.1 mol/kg
Answer: b) 2.5 mol/kg
6. What is the normality of a solution containing 5 g of NaOH in 500 mL of solution? (Molar mass of NaOH = 40 g/mol)
a) 0.2 N
b) 0.25 N
c) 0.5 N
d) 1 N
Answer: b) 0.25 N
7. The percentage by mass of solute in a solution is 20%. What is the mole fraction of the solute if the molecular mass of the solute is 50 g/mol and the molecular mass of the solvent is 18 g/mol?
a) 0.059
b) 0.121
c) 0.252
d) 0.050
Answer: a) 0.059
8. Which of the following concentration terms is affected by changes in both the solute and solvent amount?
a) Molality
b) Mole fraction
c) Molarity
d) Normality
Answer: c) Molarity
Explanation:
Molarity is the number of moles of solute per liter of solution. Since it depends on the volume of the solution (which includes both solute and solvent), any change in either the solute or solvent can affect the molarity.
9. A 5% (w/v) glucose solution contains how many grams of glucose in 500 mL of the solution?
a) 5 g
b) 10 g
c) 25 g
d) 50 g
Answer: c) 25 g
10. The molality of a solution is 3 mol/kg, and the mass of the solvent is 400 g. What is the mass of the solute?
(Molecular weight of solute = 58.5 g/mol)
a) 58.5 g
b) 70.2 g
c) 80.1 g
d) 88.2 g
Answer: b) 70.2 g
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