MDCAT ECAT Chemistry MCQs with Answers – All Units – Page 26

Question 501 s- and p-Block Elements

Which Group I metal forms mainly the normal oxide M₂O when burnt in excess oxygen?

Correct answer C. Lithium

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Question 502 s- and p-Block Elements

What mass of calcium hydroxide forms when 0.80 g of calcium reacts completely with water (Ca = 40, O = 16, H = 1)?

Correct answer B. 1.48 g

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Question 503 s- and p-Block Elements

The reactivity of Group I metals with water increases down the group mainly because ____.

Correct answer C. the first ionisation energy decreases, so the outer electron is lost more easily

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Question 504 s- and p-Block Elements

What is formed when magnesium is heated in steam?

Correct answer C. Magnesium oxide and hydrogen

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Question 505 s- and p-Block Elements

Which Group II metal reacts most vigorously with cold water?

Correct answer B. Barium

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Question 506 s- and p-Block Elements

Which Group II element does not react with water or steam under ordinary conditions?

Correct answer D. Beryllium

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Question 507 s- and p-Block Elements

What mass of magnesium oxide is formed when 4.8 g of magnesium burns completely in oxygen (Mg = 24, O = 16)?

Correct answer C. 8.0 g

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Question 508 s- and p-Block Elements

Which Group II chloride has the most covalent character?

Correct answer C. BeCl₂

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Question 509 s- and p-Block Elements

Down Group IV from carbon to lead, the stability of the +2 oxidation state ____.

Correct answer D. increases because of the inert pair effect

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Question 510 Chemical Bonding

Which statement best defines bond energy?

Correct answer C. The energy needed to break one mole of a particular bond in gaseous molecules

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Question 511 Chemical Bonding

Which order of carbon-carbon bond energies is correct?

Correct answer A. C≡C > C=C > C–C

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Question 512 Chemical Bonding

Which bond is the strongest?

Correct answer B. H–F

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Question 513 Chemical Bonding

The enthalpy change for CH₄(g) → C(g) + 4H(g) is +1664 kJ mol⁻¹. What is the average C–H bond energy?

Correct answer C. 416 kJ mol⁻¹

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Question 514 Chemical Bonding

What is the hybridisation of carbon atoms in graphite?

Correct answer C. sp²

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Question 515 Chemical Bonding

Which of the following molecules is linear?

Correct answer A. BeCl₂

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Question 516 Chemical Bonding

What is the shape of the hydronium ion, H₃O⁺?

Correct answer D. Trigonal pyramidal

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Question 517 s- and p-Block Elements

Which element of period 3 has the highest first ionisation energy?

Correct answer B. Argon

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Question 518 s- and p-Block Elements

Moving from sodium to chlorine across period 3, the atomic radius ____.

Correct answer B. decreases because effective nuclear charge increases

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Question 519 s- and p-Block Elements

Which of the following isoelectronic species has the smallest radius?

Correct answer B. Al³⁺

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Question 520 s- and p-Block Elements

Why is the first ionisation energy of aluminium lower than that of magnesium?

Correct answer A. The electron removed from Al is in a 3p orbital, which is higher in energy and partly shielded by 3s electrons

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