please someone help me with this question!!!!!! It is irritating me .

Please fast thanks in advance

Balanced equation is3 Na2SO3 + K2Cr2O7 + 4 H2SO4 --> 3 Na2SO4 + K2SO4 + Cr2(SO4)3 + 4 H2ONow , moles of Na2SO3 = 0.15 x 1 = 0.15 3 moles of Na2SO3 requires 1 mole of K2Cr2O7 .So 0.15 moles would consume 0.05 moles of K2Cr2O7 . Moles of K2Cr2O7 initially present = 0.2 x 500/1000 = 0.1So moles of K2Cr2O7 remaining = 0.1 - 0.05 = 0.05 moles