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Solutions, equilibrium and kinetics
8 NET Chemistry questions with answers and explanations.
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How many atoms are there in exactly 12 g of carbon-12?
- 1 6.022 x 10^23
- 2 12 x 6.022 x 10^23
- 3 3.011 x 10^23
- 4 6.022 x 10^22
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Correct answer: 6.022 x 10^23
12 g of carbon-12 is one mole, which contains Avogadro's number of atoms, 6.022 x 10^23.
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What is the molarity of a solution containing 98 g of H2SO4 in 1 litre of solution? (H = 1, S = 32, O = 16)
- 1 0.5 M
- 2 2 M
- 3 98 M
- 4 1 M
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Correct answer: 1 M
The molar mass of H2SO4 is 98 g/mol, so 98 g is 1 mole. In 1 litre this is 1 M.
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The elevation of the boiling point of a solution is proportional to its:
- 1 Molality
- 2 Density
- 3 Volume
- 4 Colour
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Correct answer: Molality
Boiling point elevation is a colligative property: delta Tb = Kb x molality.
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For N2 + 3H2 <-> 2NH3, the relation Kp = Kc (RT)^n has n equal to:
- 1 -2
- 2 2
- 3 -4
- 4 4
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The forward reaction of an equilibrium is exothermic. Raising the temperature will:
- 1 Shift the equilibrium to the right
- 2 Shift the equilibrium to the left
- 3 Have no effect on the equilibrium
- 4 Double the equilibrium constant
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Correct answer: Shift the equilibrium to the left
According to Le Chatelier's principle, the system opposes the added heat by favouring the endothermic, reverse reaction.
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For a first order reaction, doubling the concentration of the reactant makes the rate:
- 1 Double
- 2 Four times as large
- 3 Stay the same
- 4 Halve
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Correct answer: Double
Rate = k[A], so the rate is directly proportional to concentration.
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What is the pH of 0.1 M NaOH at 25 degrees C?
- 1 1
- 2 13
- 3 12
- 4 14
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Which of these is a Lewis acid?
- 1 NH3
- 2 H2O
- 3 BF3
- 4 OH-
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Correct answer: BF3
BF3 has an empty orbital on boron and accepts an electron pair, so it is a Lewis acid.