How much does 22.4 liters of oxygen weigh at STP ?

1 ) How much does 22.4 liters of oxygen weigh at STP ?

A ) 18 g  ,                                                   B ) 26 g  , 

C ) 32 g  ,                                                   D ) None of these ,

Correct Answer : -  C ) 32 g  ,

Solution : -

Volume = moles x STP ,

So , moles = volume / STP ,

So , moles = 22.4 / 22.4  =  1 .

So we use 2nd formula here to find mass : -

moles = mass / molecular mass ,

mass = molecular mass  x  moles ,

mass = 32 x 1,        

mass = 32   g  ,  Answer .

 

2 ) One litre oxygen gas at STP will weight : -

A ) 0.18 g  ,                                                         B ) 1.43 g  , 

C ) 3.29 g  ,                                                         D ) None of these ,

Correct Answer : -   B ) 1.43 g  , 

Solution : -

Volume = moles x STP .

So , moles = volume / STP ,

So , moles = 1 / 22.4 .

So we use 2nd formula here to find mass : -

moles = mass / molecular mass ,

mass = molecular mass  x  moles ,

mass = 32 x ( 1 / 22.4 )  ,     

mass = 1.43 g  ,  Answer .

 

3 ) The mass of one mole of electron is ?

Solution : -

mass of electron = 9.11 x 10 ^ ( - 31 ) kg .

1 mole = NA = 6.022 x 10 ^ 23 .

NA = Avagodras number .

So , formula for finding moles : -

mole = mass x NA ,

1 mole of electron = 9.11 x 10 ^ ( - 31 ) x 6.022 x 10 ^ 23  ,

1 mole of electron = 54.86 x 10 ^ ( - 5 )  ,  Answer

 

4 ) An aqueous solution of glucose is 10 % in strength .  The volume in which 1 g mole  of it is dissolved will be : -

Solution : -

10 % means if we take 10 g glucose = ( 10 / 180 )  mole glucose will present in 0.1 L solution or 100 cc .

So , ( 10 / 180 ) mole ---------> 0.1 L ,

1 g mole = ( 0.1 x 180 L ) / 10 = 1.8 L .

OR

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