The complete combustion of a mixture of carbon and silicon dioxide consumed oxygen weighing 22.4 g. What volume of a 20% potassium

The complete combustion of a mixture of carbon and silicon dioxide consumed oxygen weighing 22.4 g. What volume of a 20% potassium hydroxide solution (density 1.173 g / ml) can react with the initial mixture if it is known that the mass fraction of carbon in it is 70% ?

C + O2 = CO2
SiO2 + O2 ≠ (no reaction)
n (O2) = 22.4 / 32 = 0.7 mol
n (O2) = n (C) = 0.7 mol = 70% ⇒ n (SiO2) = 0.3 mol
n (KOH) = (0.2 x 1.173 x V) / 56 = 0.6
⇔ V = 143 ml or 0.143 L.
Answer: 0.143 L of potassium hydroxide can react with the original mixture.

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