Question

1. Electron has mass. But mass number of an atom does not conclude the electron. Why?

2. There are 12.046 x 1023 atoms of calcium at STP condition in a container?

a) What is the volume of the container?

b) How many molecules of CO2 needed to fill that same container at STP.

3. Calculate the % relative abundance of B-10 and B-11. If the Average atomic mass is 10.804

amu.

4. Calculate the vapour density of methane?

5. Calculate the density of 1 mole of CO2 at STP.

6. Why do atoms forms molecules?

7. Why do we use unit amu to measure the mass of atoms (or) molecules?

8. What is the need of the average atomic mass of an element?

9. Under same conditions of temperature and pressure if you collect 3 litre of O2 , 5 litre of Cl2

and 6 litre of H2 .

i) Which has the highest number of molecules?

ii) Which has the lowest number of molecules?

10. Calculate the number of water molecules present in one drop of water . Which weights

0.18g

11. Give a single team substitute for each of the following.

i) 6.023 x 1023 molecules

ii) 22.4 litres of gas at STP

iii) Half of relative molecular mass

iv) 1/12 th part of the mass of one atom of carbon

12. If one mole of carbon atoms weigh 12 gram, what is the mass (in green) of 1 atom of

carbon?

13. A 0.24g sample of compound of oxygen and boron was found by analysis to contain 0.076g

of boron 0.144g of oxygen. Calculate the percentage composition of the compound by

weight.

14. Calculate the number of molecules of sulphur (S8) present in 16g of solid sulphur?

15. Calculate the number of aluminium ions preset in 0.051g of Al2 O3. (Hint : The mass of an

ion is the same as that of an atom of the same element. At. Mass of Al = 27 u)

16. The visible universe is estimated to contain 1022 stars. How many moles of stars are

present in the visible universe?

17. A gold sample contains 90 % of gold and the rest copper. How many atoms of gold are

present in one gram of this sample of gold?​

Answer 1

Answer:

The mass of electron is much lesser than proton and neutrons