At a given moment the reaction quotient Qc of a reaction is smaller than Kc. What will happen as the system moves to equilibrium?
Correct answer D. The net reaction proceeds in the forward direction
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MDCAT ECAT Chemistry MCQs
Page 32 of MDCAT ECAT Chemistry multiple-choice questions with answers. Tap an option to check yourself.
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- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
In the Haber process, ammonia is liquefied and removed from the gas mixture. What is the effect on the equilibrium?
Correct answer C. The equilibrium shifts forward, producing more ammonia
The equilibrium constant for A + B ⇌ C is Kc. What is the equilibrium constant for C ⇌ A + B at the same temperature?
Correct answer D. 1/Kc
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For an exothermic reversible reaction, what happens to the equilibrium constant when the temperature is raised?
Correct answer C. It decreases
Which set of conditions is typically used in the Haber process for the industrial manufacture of ammonia?
Correct answer D. About 450 °C, about 200 atm and an iron catalyst
Why is a temperature of about 450 °C used in the Haber process even though a lower temperature gives a higher equilibrium yield of ammonia?
Correct answer D. At lower temperatures the rate of reaction becomes too slow to be economical
What is the correct solubility product expression for silver chromate, Ag₂CrO₄?
Correct answer B. Ksp = [Ag⁺]²[CrO₄²⁻]
The solubility of AgCl in pure water at 25 °C is 1.3 × 10⁻⁵ mol dm⁻³. What is its solubility product?
Correct answer B. 1.7 × 10⁻¹⁰ mol² dm⁻⁶
The solubility of CaF₂ at a certain temperature is 2.0 × 10⁻⁴ mol dm⁻³. What is its Ksp?
Correct answer C. 3.2 × 10⁻¹¹ mol³ dm⁻⁹
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What is observed when a few crystals of NaCl are added to a saturated solution of AgCl?
Correct answer B. Some AgCl precipitates because its solubility is lowered
The Ksp of AgCl is 1.8 × 10⁻¹⁰ mol² dm⁻⁶. What is its molar solubility in 0.10 mol dm⁻³ NaCl solution?
Correct answer A. 1.8 × 10⁻⁹ mol dm⁻³
Which mixture in water forms an acidic buffer solution?
Correct answer B. Ethanoic acid and sodium ethanoate
Which pair of substances is used to prepare a basic buffer?
Correct answer A. NH₄OH and NH₄Cl
In an ethanoic acid / sodium ethanoate buffer, how is a small amount of added H⁺ removed?
Correct answer B. It combines with CH₃COO⁻ ions to form undissociated CH₃COOH
A buffer contains ethanoic acid (pKa = 4.74) and sodium ethanoate in which / = 10. What is its pH?
Correct answer D. 5.74
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Calcium carbonate exists as both calcite and aragonite. This phenomenon is called ____
Correct answer D. polymorphism
When a crystalline solid is cut with a sharp edge, it splits along definite smooth surfaces. These are called ____
Correct answer D. cleavage planes
Why does solid iodine sublime easily on gentle heating while sodium chloride does not?
Correct answer A. I₂ molecules are held by weak London forces, whereas NaCl has strong ionic bonds
Using ΔHf(NaCl) = −411, ΔHsub(Na) = +108, IE(Na) = +496, ½BDE(Cl₂) = +121 and EA(Cl) = −349 kJ mol⁻¹, what is the lattice energy of NaCl?
Correct answer B. −787 kJ mol⁻¹
What is the coordination number of each ion in the caesium chloride crystal?
Correct answer B. 8