Answer to Question #107337 in General Chemistry for Chisom

Question

What volume of oxygen measured at s.t.p would be required for complete combustion of all hydrogen evolved by reacting 12g of magnesium with excess tetraoxosulphate(vi) acid

Answer 1

Here,tetraoxosulphate(vi) acid is sulphuric acid whose reaction with magnesium is

$Mg+H_2SO_4\longrightarrow MgSO_4+H_2(g)$

Here sulphuric acid is in excess whereas Mg mass is given as 12 g

moles of Magnesium is = $\frac{given mass}{molar mass}=\frac{12}{24}=0.5 mole$

since from above reaction 1 mole of Magnesium givesn 1 mole of hydrogen so, moles of

hydrogen gas produced= 0.5 mole

Now, it is combustion with oxygen so the reaction will be as follows

$2H_2+O_2\longrightarrow 2H_2O$

From above reaction we can say that 2 mole of hydrogen react 1 mole oxygen

so 0.5 mole of hydrogen will react with 0.25 mole of Oxygen.

We know that at STP 1 mole of gas has volume = 22.4 L

so, volume of oxygen require= $22.4\times0.25=5.6 L$

So, volume of oxygen required = 5.6 L