1.

How many moles of Na are present in 120 g Sodium sulphate.

Answer»

Molar mass of Sodium sulphate (Na2​​​​​​SO4)-

= 2(23)+32+4(16)

= 46+32+64 

= 142 g/mol

Number of moles of Na​​​​​​2SO4 in 120 grams of it:

No. of moles = Molecular mass/ Molar mass

No. of moles = 120/142 = 0.845 moles

Now, in each mole of sodium sulphate, there are 2 moles of Sodium (Na). Therefore, 0.845×2 = 1.69 moles of sodium are present in 120 grams of sodium sulphate.

Na2SO4(sodium sulphate)

Molecular weight - 142 g/mol

Number of moles of sodium sulphate = \(\frac{120g}{142g/mol} = 0.84 mole\) 

\(\because\) 1 molecule of Na2SO4 contains  = 2 atom of sodium

\(\therefore\) 0.84 mole of Na2SO4 contain = 1.68 moles sodium atom.

Hence, 120 g Na2SO4 contain 1.68 moles sodium atom



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