18 carat gold contains from Chemistry JEE Year 2007 Free Solved

Subject

Chemistry

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction?

  • Endothermic and decreasing disorder

  • Exothermic and increasing disorder

  • Endothermic and increasing disorder

  • Exothermic and decreasing disorder


22.

Identify the correct statement for change of Gibbs energy for a system (Gsystem) at constant temperature and pressure

  • If Gsystem = 0, the system has attained equilibrium

  • If Gsystem = 0, the system is still moving in a particular direction

  • If Gsystem = 0, the process is not spontaneous

  • If Gsystem = 0, the process is spontaneous


23.

The standard emf of a galvanic cell involving cell reaction with n = 2 is found to be 0.295 V at 25°C. The equilibrium constant of the reaction would be

  • 2.0 × 1011

  • 4.0 × 1012

  • 1.0 × 102

  • 1.0 × 1010


24.

nXemit one α and two β- particles. It is converted into

  • nXm - 4

  • n - 1Xm - 1

  • nZm - 4

  • None of these


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25.

18 carat gold contains

  • 18% gold

  • 24% gold

  • 75% gold

  • 60% gold


C.

75% gold

The weight of gold in jewellery is expressed in carats. It simply implies the number of parts by weight of gold in 24 parts by weight of the alloy.

Pure gold is 24 carats. 18 carat gold means that it contains 18 parts by weight ofpure gold in 24 parts by weight of the alloy.

% of gold = 1824 × 100

% of gold = 75%


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26.

Which of the following metals will not form an amalgam?

  • Gold

  • Silver

  • Zinc

  • Iron


27.

The element which liberates oxygen gas from water is

  • P

  • Na

  • F

  • I


28.

Which is the weakest acid out out of HF, HCl, HBr and HI?

  • HF

  • HCl

  • HBr

  • HI


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29.

The strongest oxidising agent amongst F2, Cl2, Br2 and I2 is

  • F2

  • I2

  • Cl2

  • Br2


30.

A compound has the empirical formula CH2O. Its vapour density is 30. Its molecular formula is

  • C2H4O2

  • C2H6O

  • C2H6O2

  • C2H4O


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