Question

Calculate the number of moles in I. 81g of aluminium II. 4.6 g sodium III. 5.1g of Ammonia IV. 90 g of water V. 2 g of NaOH

Answer 1

first of all
mole =given weight/molecular weight
i) mole of Aluminum=81/27=3

ii)mole of sodium=4.6/23=0.2

iii) mole of amonia=5.1/17=0.3

iv) mole of water=90/18=5

v) mole of NaOH=2/40=0.05

Answer 2

Answer:

1. 3 moles
2. 0.2 moles
3. 0.3 moles
4. 5 moles
5. 0.05 moles

Explanation:

The formula of No. of moles (n) is   $\frac{Given mass (w)}{Molecular mass (M)}$

1. No. of moles in 81 gms of aluminium (Al) =    $\frac{81}{27}$    = 3
2. No. of moles in 4.6 gms of sodium (Na) =    $\frac{4.6}{23}$    = 0.2
3. No. of moles in 5.1 gms of ammonia (NH₄) =    $\frac{5.1}{17}$    = 0.3
4. No. of moles in 90 gms of water (H₂O)  =    $\frac{90}{18}$    = 5
5. No. of moles in 2 gms of sodium hydroxide (NaOH) =    $\frac{2}{40}$   = 0.05

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