Let’s find the amount of potassium substance by the formula:
n = m: M.
M (K) = 39 g / mol.
n = 117 g: 39 g / mol = 3 mol.
Let’s compose the reaction equation. Let’s find the quantitative ratios of substances.
4K + O2 = 2K2O.
For 4 mol of potassium, there are 2 mol of potassium oxide.
The substances are in quantitative ratios of 4: 2 or 2: 1.
The amount of potassium oxide substance will be 2 times less than the amount of potassium substance.
n (K2O) = 1 / 2n (K) = 0.3: 2 = 1.5 mol.
Find the mass of potassium oxide.
m = n × M.
M (K2O) = 39 × 2 + 16 = 94 g / mol.
m = 94 g / mol × 1.5 mol = 141 g.
Answer: 141 g.
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