How many molecules of water are present in a drop of water which has a mass of 50mg?
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1 mole of water has 6.023×10^23 molecules.
now 1 mole of water weighs 18g.
then,let x moles of water weighs 50mg=50×10^-3 g.
so 1 mole ----------> 18g
x mole-------> 50×10^-3 g
1×50×10^-3=x×18
x=50×10^-3/18
x=2.78×10^-3
x=0.00278 moles
hence the total no. of molecules present in a drop of water which has mass of 50mg are
=0.00278×6.023×10^23
=0.0167×10^23
=1.67×10^21
now 1 mole of water weighs 18g.
then,let x moles of water weighs 50mg=50×10^-3 g.
so 1 mole ----------> 18g
x mole-------> 50×10^-3 g
1×50×10^-3=x×18
x=50×10^-3/18
x=2.78×10^-3
x=0.00278 moles
hence the total no. of molecules present in a drop of water which has mass of 50mg are
=0.00278×6.023×10^23
=0.0167×10^23
=1.67×10^21
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