When acidified MnO₄⁻ oxidises Fe²⁺ to Fe³⁺ (MnO₄⁻ being reduced to Mn²⁺), what is the mole ratio Fe²⁺ : MnO₄⁻ in the balanced equation?
Correct answer C. 5 : 1
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MDCAT ECAT Chemistry MCQs
Page 29 of MDCAT ECAT Chemistry multiple-choice questions with answers. Tap an option to check yourself.
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- Gases 40
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- Chemical Bonding 39
- Alcohols and Phenols 38
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In acidic solution Cr₂O₇²⁻ oxidises Fe²⁺ to Fe³⁺ and is reduced to Cr³⁺. How many Fe²⁺ ions react with one Cr₂O₇²⁻ ion?
Correct answer A. 6
When the equation Cu + HNO₃ → Cu(NO₃)₂ + NO + H₂O (dilute acid) is balanced with the smallest whole numbers, what is the coefficient of HNO₃?
Correct answer A. 8
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What is the standard enthalpy of formation of O₂(g) at 298 K?
Correct answer B. 0 kJ mol⁻¹
Which statement best defines the standard enthalpy of combustion of a substance?
Correct answer D. The enthalpy change when one mole of the substance burns completely in excess oxygen under standard conditions
Why is the enthalpy of neutralisation of ethanoic acid by NaOH less negative than that of HCl by NaOH?
Correct answer B. Some energy is used to ionise the weak acid fully
When a reaction is carried out in 50.0 g of water, the temperature rises by 6.0 °C. Taking c = 4.18 J g⁻¹ K⁻¹, how much heat is released?
Correct answer B. 1254 J
Using bond energies H–H = 436, Cl–Cl = 243 and H–Cl = 432 kJ mol⁻¹, what is ΔH for H₂(g) + Cl₂(g) → 2HCl(g)?
Correct answer C. −185 kJ mol⁻¹
How is the lattice energy of an ionic compound such as NaCl usually obtained?
Correct answer C. Indirectly, from a Born-Haber cycle using Hess's law
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What is meant by the heat capacity of a body?
Correct answer D. The heat required to raise its temperature by 1 K
Which statement about the internal energy, U, of a system is correct?
Correct answer C. It is the total kinetic and potential energy of its particles, and only changes in it can be measured
When a gas in a cylinder is compressed by a piston, what are the signs of the work done (w) and its effect on the internal energy of the gas, if no heat is exchanged?
Correct answer D. w is positive and internal energy increases
Given standard enthalpies of formation CH₄(g) = −74.8, CO₂(g) = −393.5 and H₂O(l) = −285.8 kJ mol⁻¹, what is ΔH for CH₄ + 2O₂ → CO₂ + 2H₂O(l)?
Correct answer B. −890.3 kJ mol⁻¹
Which compound is expected to have the most exothermic lattice energy?
Correct answer B. MgO
Which equation represents the standard enthalpy of formation of liquid water?
Correct answer D. H₂(g) + ½O₂(g) → H₂O(l)
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A reaction has an activation energy of 120 kJ mol⁻¹ in the forward direction and 160 kJ mol⁻¹ in the reverse direction. What is ΔH for the forward reaction?
Correct answer D. −40 kJ mol⁻¹
For which reaction is ΔH equal to ΔU at constant temperature?
Correct answer A. H₂(g) + Cl₂(g) → 2HCl(g)
Which statement about the energy of bond breaking and bond making is correct?
Correct answer D. Breaking bonds absorbs energy and forming bonds releases energy
In a multi-step reaction mechanism, which step controls the overall rate of reaction?
Correct answer D. The slowest step
Which statement is true for an exothermic reaction?
Correct answer C. ΔH is negative and heat is released to the surroundings