Recognize, using qualitative reactions, each of the proposed substances issued in the form of solutions: hydrochloric acid

Recognize, using qualitative reactions, each of the proposed substances issued in the form of solutions: hydrochloric acid, potassium chloride, sulfuric acid. What mass of potassium hydroxide KOH should be taken to neutralize a solution containing 9.8 g of phosphoric acid to a medium salt?

1) HCl – Na2CO3 (gas evolution)
KCl – AgNO3 (white curdled precipitate)
H2SO4 – Ba (NO3) 2 (white precipitation)
2) H3PO4 + 3KOH = K3PO4 + 3H2O
n (H3PO4) = 9.8g / 98 g / mol = 0.1 mol
n (KOH) = 3n (H3PO4) = 0.3 mol
m (KOH) = 0.3 mol * 56 g / mol = 16.8 g
Answer: 16.8 g