1) calculate the number of molecules in 50g of calcium carbonate

2) calculate the number of moles for the following.

a.64g of oxygen atom

b.24*10 powered by 23 number of oxygen atom

3)calculate the formula unitmass of

a) calcium chloride b) sodium sulphite c) ammonium carbonate

4) calculate the no. of moles sulphur (Sg) present in 16g of solid sulphur

5) write the chemical formula using criss cross method

a)ammonium sulphate b)sodium sulphate c) barium nitrate

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A-1) Number of molecules in 50g of calcium carbonate:

 Number of molecules = ( mass / molar mass) * avogadro number

 = (50 / 100) * 6.023*10²³

 = 3.0115*10²³ molecules

A-3, a)  Formula unit mass of calcium chloride:

 Mass of Ca = 40g

 Mass of Cl = 35.5

 So, mass of CaCl₂ = 40 + ( 2* 35.5)

 = 111 g mol^-1

A-5, a) Chemical formula of Ammonium sulphate:

 NH₄  SO₄

 +1  -2

 Formula - (NH₄)₂SO₄