Question

calculate the molar mass of 1.magnesium sulphate 2.sodium carbonate and identify the polyatomic ion present in each of them

Answer 1

molecular formula of sodium sulphate =Na2(SO4)

atomic mass of Na =23 g
atomic mass of S = 32 g
atonic mass of O = 16 g

so, molecular mass = 23 ×2 + 32 +16×4
= 46 + 32 + 64 = 142 g

poly atomic ion in Na2(SO4) is SO4--

molecular formula of sodium carbonate= Na2CO3

atomic mass of C = 12 g

so , molecular mass = 46 + 12 +48
= 106 g
polyatomic ions in Na2CO3 is CO3--

Answer 2

Magnesium sulphate=MgSO4
                                 =1(24)+1(96)
                                 =24+96
                                 =120
Sodium carbonate=Na2CO3
                             =2(22)+1(12)+3(16)
                             =44+12+48
                             =104