Chemistry Class 11 NCERT Solutions: Chapter 2 Structure of Atom Part 1

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Q: 1. (i) Calculate the number of electrons which will together weigh one gram.

(ii) Calculate the mass and charge of one mole of electrons.

Answer:

(i) Mass of one electron

Number of electrons that will weigh

(ii) Mass of one electron

Mass of one mole of electron

Charge on one electron

Charge on one mole of electron

Q: 2

(i) Calculate the total number of electrons present in one mole methane.

(ii) Find (a) the total number and (b) the total mass of neutrons in 7 of

(Assume that mass of a neutron ).

(iii) Find (a) the total number and (b) the total mass of protons in Will the answer change if the temperature and pressure are changed?

Answer:

(i) Number of electrons present in 1 molecule of methane

Number of electrons present in 1 mole i.e., molecules of methane

(ii) (a) Number of atoms of in 1 mole

Since 1 atom of contains i.e., 8 neutrons, the number of neutrons in or,

Number of neutrons in

(b) Mass of one neutron

Mass of total neutrons in

(iii) (a) 1 mole of

Total number of protons present in 1 molecule of

Number of protons in molecules of

Number of protons in 34

(b) Mass of one proton

Total mass of protons in 34

The number of protons, electrons, and neutrons in an atom is independent of temperature and pressure conditions. Hence, the obtained values will remain unchanged if the temperature and pressure is changed.