SAMPLE NUST NET 2 CHEMISTRY QUESTIONS

ELECTROCHEMISTRY

QUESTION:

The oxidation of oxygen in peroxides is?

OPTIONS:

  • +1
  • -1
  • +2
  • -2

CORRECT OPTION:

-1

EXPLANATION:

Peroxides include hydrogen peroxide, H2O2. This is an electrically neutral compound and so the sum of the oxidation states of the hydrogen and oxygen must be zero.

THERMOCHEMISTRY

QUESTION:

2 moles of helium gas are expanded isotherm-ally and irreversibly at 270C from volume 1 dm3 to 1 m3 at a constant pressure of 100 kPa. Calculate the work done?

OPTIONS:

  • 99900 KJ
  • 99900 J
  • 34464 KJ
  • 34464 J

CORRECT ANSWER:

99900 J

EXPLANATION:

BASICS OF CHEMISTRY

QUESTION:

Non-stoichiometric compounds are formed by:

OPTIONS:

  • Only alkali metals
  • Only transition elements
  • Only noble gases
  • None of the above

CORRECT OPTION:

Only transition elements

EXPLANATION:

Binary transition metal compounds, such as the oxides and sulfides, are usually written with idealized stoichiometry’s, such as FeO or FeS but these compounds are usually cation deficient and mostly never contain a 1:1 cation:anion ratio. Thus a substance such as ferrous oxide is actually a nonstoichiometric compound with a range of compositions.

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