The hardness of a water sample containing 10^–3M MgSO₄ expressed as CaCO₃ equivalents (in ppm) is $\mathrm{\_\_\_\_}$ (molar mass of MgSO₄ is 120.37 g/mol)

10⁻³ molar MgSO4​=10⁻³ moles of MgSO_4​ present in 1 Litre.

 moles of CaCO3  ​​= moles of MgSO4​​

PPM (in term of CaCO₃​)=$\frac{10{ }^{-3}\times 100}{1000}\times {10}^6$ =100 ppm