Question

Borax in water reacts according to the following equation:

$B_4{O}_7^{2-}+7H_{2}O\to 4H_{3}B{O}_3+2O{H}^{-}$

Amount of borax (${Na}_2{B}_4{O}_7\cdot 10H_{2}O$) (in grams) which is required to prepare $50$ ml of $0.2M$ solution is (as nearest integer):

Answer 1

Molecular weight of borax = 382

Mole of borax in solution, n = molarity x volume = 0.01 moles

So, 0.01 moles of borax is required

Amount of borax = moles $\times$ molar mass

Amount of borax =$382\ast 0.01=3.82g\approx 4g$