Answers

2016-03-17T16:24:56+05:30
No of molecules = moles x avagadro numberĀ 

moles = given mass / molar mass = 18/18 = 1 mole

no of molecules = 1x6.022x 10^{23} = 6.022x 10^{23}
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hope this will help .... and it is an imp question ... as it was asked in my science sa2 exam!!