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1009 available questions

Chemistry · Question 751

How many moles are present in 6.0 g of carbon-12?

  1. 0.25 mol
  2. 0.50 mol
  3. 1.0 mol
  4. 2.0 mol
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Correct answer: B

0.50 mol

n = m/M = 6.0/12.0 = 0.50 mol.

Chemistry · Question 752

What is the first member of the alkene homologous series?

  1. Methane
  2. Ethene
  3. Ethyne
  4. Propene
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Correct answer: B

Ethene

An alkene requires a carbon-carbon double bond, so the smallest member is ethene.

Chemistry · Question 753

Compounds with the same molecular formula but different carbon-chain arrangements show:

  1. Position isomerism
  2. Chain isomerism
  3. Functional-group isomerism
  4. Geometrical isomerism
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Correct answer: B

Chain isomerism

Different branching of the carbon skeleton is chain isomerism.

Chemistry · Question 754

Breaking large hydrocarbon molecules into smaller ones is called:

  1. Cracking
  2. Reforming
  3. Hydrogenation
  4. Polymerization
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Correct answer: A

Cracking

Cracking splits long hydrocarbon chains into smaller alkanes and alkenes.

Chemistry · Question 755

Which number measures the anti-knock quality of petrol?

  1. Cetane number
  2. Octane number
  3. Mass number
  4. Iodine number
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Correct answer: B

Octane number

Octane number measures a petrol's resistance to engine knocking.

Chemistry · Question 756

What is the first member of the alkyne homologous series?

  1. Methyne
  2. Ethene
  3. Ethyne
  4. Propyne
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Correct answer: C

Ethyne

A carbon-carbon triple bond needs at least two carbon atoms, so ethyne is first.

Chemistry · Question 757

How many structural chain isomers does butane have?

  1. One
  2. Two
  3. Three
  4. Four
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Correct answer: B

Two

Butane exists as n-butane and 2-methylpropane.

Chemistry · Question 758

At equilibrium in a closed system of constant temperature and volume, reactant and product concentrations:

  1. Become zero
  2. Remain constant
  3. Increase indefinitely
  4. Alternate periodically
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Correct answer: B

Remain constant

Equal forward and reverse rates keep macroscopic concentrations constant.

Chemistry · Question 759

Approximately how much energy is required to remove the first electron from one mole of gaseous sodium atoms?

  1. 49.6 kJ mol−1
  2. 496 kJ mol−1
  3. 960 kJ mol−1
  4. 1496 kJ mol−1
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Correct answer: B

496 kJ mol−1

The first ionization energy of sodium is approximately 496 kJ mol−1.

Chemistry · Question 760

Isotopes of an element have similar chemical properties but different:

  1. Atomic numbers
  2. Numbers of protons
  3. Mass numbers
  4. Valence-electron arrangements
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Correct answer: C

Mass numbers

Isotopes have the same proton number but different neutron counts and therefore different mass numbers.