Mass = 20 gMagnesium Sulphate (MgSo₄) To find :Number of moles According to the QUESTION, At first we will find the molar mass of MgSO₄⇢ Atomic Mass of Magnesium (Mg) = 24 u⇢ Atomic Mass of SULPHUR (S) = 32 u⇢ Atomic Mass of Oxygen (O) = 16 uNow we calculate the molecular mass Magnesium Sulphate, ⇢ 24 + 32 + 16 × 4 ⇢ 120 uWe know,⇢ Number of moles = Given mass ÷ Molar mass⇢ Number of moles = 20 ÷ 120⇢ Number of moles = 0.167So,the number of moles is 0.167._____________________________ More details :-MOLE of Atoms :1 mole of atoms of an element has a mass equal to the gram atomic mass of the element.Mole of Molecules :1 mole of molecules of a substance has a mass equal to the gram molecular mass of the substance. Gram Atomic Mass :The amount of a substance whose mass in gram is NUMERICALLY equal to its atomic mass is called gram atomic mass of that substance. Gram Molecular Mass :The amount of a substance whose mass in gram is numerically equal to its molecular mass is called gram molecular mass of that substance.