Question

Au+H2SO4= Ba(OH)2+H2SO4= K2O+H2SO4= Fe+H2SO4=

Answer 1

$Au + H_2SO_4 \neq$ - растворяется только в царской водке(HCl + HNO₃) 
$Ba(OH)_2 + H_2SO_4 = BaSO_4 + 2H_2O$ - разбавленная серная кислота
$K_2O + H_2SO_4 = K_2SO_4 + H_2O$ - разбавленная серная кислота
$Fe + H_2SO_4 = FeSO_4 + H_2$ - разбавленная серная кислота
$2Fe + 6H_2SO_4 = Fe_2(SO_4)_3 + 3SO_2 + 6H_2O$ - концентрированная серная кислота, ПРИ НАГРЕВАНИИ!!!!!

Answer 2

It looks like you've provided a series of chemical reactions, but some of them are incomplete. I'll complete the reactions for you:

1. Au + H2SO4 → No reaction (Gold does not react with sulfuric acid under normal conditions.)

2. Ba(OH)2 + H2SO4 → BaSO4 + 2H2O (Barium hydroxide reacts with sulfuric acid to form barium sulfate and water.)

3. K2O + H2SO4 → K2SO4 + H2O (Potassium oxide reacts with sulfuric acid to form potassium sulfate and water.)

4. Fe + H2SO4 → FeSO4 + H2 (Iron reacts with sulfuric acid to form ferrous sulfate and hydrogen gas.)