How many grams of HCl would react with 5 grams on MnO2, if Mn=55u and Cl=35.5u ?
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Solution
​4HCl(aq) + ​MnO2(s) ​ ​2H2O(l) + ​MnCl2(aq) + ​Cl2(g).
number of moles 4 1 2 1 1
molecular mass of HCl = 1 + 35.5 = 36.5g/mol
molecular mass of ​MnO2 ​ = 55 + 2x 16 = 87g/mol
1 mole of ​MnO2 reacts with = 4 moles of HCl
ie 87 g of MnO2reacts with = (4x36.5) g of HCl
1g ​of MnO2 reacts with = (4x36.5)/87 g of HCl 5g of ​of MnO2 reacts with = (4x36.5x5)/87 g of HCl = 8.39 g of HCl