Chemistry Class 11 NCERT Solutions: Chapter 5 States of Matter Part 4

Q: 10. Equation of phosphorus vapour weighs Equation bar pressure. What is the molar mass of phosphorus?

Answer:

Given,

Equation

Equation

Equation

Equation

The number of moles (n) can be calculated using the ideal gas equation as:

Equation

Equation

Equation

Therefore, molar mass of phosphorus Equation

Hence, the molar mass of phosphorus is Equation

Q: 11. A student forgot to add the reaction mixture to the round bottomed flask at Equation but instead he/she placed the flask on the flame. After a lapse of time, he realized his mistake, and using pyrometer, he found the temperature of the flask was Equation . What fraction of air would have been expelled out?

Answer:

Let the volume of the round bottomed flask be V.

Then, the volume of air inside the flask at Equation is Equation .

Now,

Equation

Equation

Equation

Equation

According to Charles’s law,

Equation

Equation

Equation

Equation

Therefore, volume of air expelled out Equation

Hence, fraction of air expelled out Equation

Q: 12. Calculate the temperature of 4.0 mol of gas occupying Equation Equation

Answer

Given,

Equation

Equation

Equation

Equation

The temperature (T) can be calculated using the ideal gas equation as:

Equation

Equation

Equation

Equation

Hence, the required temperature is Equation .

Q: 13. Calculate the total number of electrons present in Equation of dinitrogen gas.

Answer:

Molar mass of dinitrogen Equation

Equation

Equation

Equation

Now, Equation molecule of Equation contains 14 electrons.

Therefore, Equation molecules of Equation contains =14× 3.01× 1023

Equation electrons

Q: 14. How much time would it take to distribute one Avogadro number of wheat grains, if Equation grains are distributed each second?

Answer:

Avogadro number Equation

Thus, time required

Equation

Equation

Equation

Hence, the time taken would be Equation

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