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

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 Equation

Equation

Number of electrons that will weigh Equation

Equation

Equation

Equation

Equation

(ii) Mass of one electron Equation

Mass of one mole of electron Equation

Equation

Charge on one electron Equation

Charge on one mole of electron Equation

Equation

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 Equation of Equation

(Assume that mass of a neutron Equation ).

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

Answer:

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

Equation

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

Equation

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

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

Number of neutrons in Equation

Equation

Equation

(b) Mass of one neutron Equation

Mass of total neutrons in Equation

Equation

Equation

(iii) (a) 1 mole of Equation

Equation

Equation

Total number of protons present in 1 molecule of Equation

Equation

Equation

Number of protons in Equation molecules of Equation

Equation

Equation

Equation

Number of protons in 34 Equation

Equation

Equation

(b) Mass of one proton Equation

Total mass of protons in 34 Equation

Equation

Equation

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.

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