71. What is the molality of a solution prepared by dissolving 10 g of NaOH in 500 g of water?
(Molecular weight of NaOH = 40 g/mol)
a) 0.25 mol/kg
b) 0.5 mol/kg
c) 1 mol/kg
d) 2 mol/kg
Answer: c) 0.5 mol/kg
72. Which concentration term is suitable when dealing with temperature changes?
a) Molarity
b) Molality
c) Normality
d) Weight percent
Answer: b) Molality
Explanation:
Molality is based on the mass of the solvent, which remains unaffected by temperature, making it ideal for situations involving temperature changes.
73. What is the molarity of a solution prepared by dissolving 20 g of NaOH in 250 mL of solution?
(Molecular weight of NaOH = 40 g/mol)
a) 0.5 M
b) 1 M
c) 2 M
d) 4 M
Answer: c) 2 M
74. The molality of a solution is expressed as:
a) Moles of solute per liter of solvent
b) Moles of solute per kilogram of solvent
c) Moles of solute per liter of solution
d) Moles of solute per milliliter of solution
Answer: b) Moles of solute per kilogram of solvent
Explanation:
Molality is defined as the number of moles of solute dissolved in 1 kilogram of solvent.
75. What is the normality of a 2 M H₂SO₄ solution?
a) 1 N
b) 2 N
c) 3 N
d) 4 N
Answer: d) 4 N
76. What is the mole fraction of ethanol in a solution containing 46 g of ethanol and 180 g of water?
(Molecular weight of ethanol = 46 g/mol, water = 18 g/mol)
a) 0.2
b) 0.33
c) 0.5
d) 0.67
Answer: a) 0.2
77. If the molality of a solution is 2 mol/kg, how many moles of solute are present in 4 kg of solvent?
a) 1 mol
b) 2 mol
c) 4 mol
d) 8 mol
Answer: d) 8 mol
78. What is the molarity of a solution prepared by dissolving 10 g of NaOH in 2 L of solution?
(Molecular weight of NaOH = 40 g/mol)
a) 0.1 M
b) 0.125 M
c) 0.25 M
d) 0.5 M
Answer: a) 0.125 M
79. Which of the following solutions will have the highest osmotic pressure at the same concentration?
a) Glucose solution
b) NaCl solution
c) K₂SO₄ solution
d) Urea solution
Answer: c) K₂SO₄ solution
Explanation:
Osmotic pressure is directly proportional to the number of particles in solution. K₂SO₄ dissociates into 3 ions (2 K⁺ and SO₄²⁻), which gives the highest number of particles and, therefore, the highest osmotic pressure.
80. The molarity of a solution changes with:
a) Pressure
b) Volume
c) Temperature
d) Solute amount
Answer: c) Temperature
Explanation:
Molarity depends on the volume of the solution, which changes with temperature, making it temperature-dependent.
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