IGCSE Chemistry Paper-1: Specimen Questions with Answers 56 - 58 of 99

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Question 56

Question

MCQ▾

Three elements Chlorine, Bromine and iodine have similar properties and they form a Dobereiner՚s triad. If the atomic mass of chlorine is 35.5 and that of iodine is 126.9. What will be the atomic mass of Bromine (approx. value)

Choices

Choice (4)

a.

Insufficient data

b.

99.9

c.

79.9

d.

89.9

Answer

c.

Explanation

According to Dobereiner՚s triad

Atomic mass of Bromine = Average of atomic masses of Cl and I

Now, = Average of atomic masses of Cl and I =

Therefore 79.9 will be the atomic mass.

Question 57

Question

MCQ▾

Electron configuration of an element X is 1s22s22p63s23p64s23d3, which one of the following statements are true for X element.

  • Period number of X is 4 and it is transition element
  • X is a non metal
  • Valence electrons of X are in “s” and “d” shells.

Choices

Choice (4)

a.

i and iii

b.

i and ii

c.

ii and iii

d.

All of the above

Answer

a.

Explanation

X element has electron configuration;

X: 1s22s22p63s23p64s23d3

Period of the element is equal to highest energy level of electrons or principal quantum number.

Therefore, X is in period 4

The group to which it belong will be 3 + 2 = 5 B group. Therefore is a metal

Question 58

Question

MCQ▾

Which of the following is a type of decomposition reaction:

Choices

Choice (4)

a.

Displacement

b.

Thermal

c.

Electric

d.

All of the above

Answer

b.

Explanation

The reaction in which heat energy is given to the substance and substance breaks into two or more simpler substances is called thermal decomposition reaction.

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