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# volume of a gas at STP is 1.12 into 10^-7. calculate the no of molecules in it?

options are:-

a) 3.01 into 10^20

b)3.01 into 10^12

c)3.01 into 10^23

d)6.02 into 10^12

how to solve this problem. please help??

volume is in cc.

### 3 Answers

- AnthonyLv 78 years agoFavorite Answer
1 mole of gas occupies 22.4 litres at STP

1 mole of gas contains Avogadros number of molecules = 6.022*10^23.

You have not given any units for the volume.

The answer would be (volume/22.4)*Avogadros number = (1.12*10^-7/22.4)*6.022\*10^34

= 0.3011*10^27 if volume is in litres

=0.3011*10^24 = 3.011*10^23 if volume is in m^3.

Answer is c).

- 5 years ago
Certainly option B is correct

We know that 1L= 1000cc and at STP the no of particles present in 22.4L of solution is equal to the Avogadro number.

Therefore,

22.4*10^3-----> 1 mole

Then, 1.12*10^-7= 1.12*10^-7/ 22.4*10^3

=1/20 * 10 ^-10

= 5*10^-9 moles

Now, we know that mole has 6.022*10^23 molecules

5*10^-9 moles has = 6.022*10^23 * 5*10^-9 moles

~ 3.01* 10 ^12