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??

Update:

volume is in cc.

3 Answers

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  • 8 years ago
    Favorite 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

  • 5 years ago

    B is the correct ans

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