15.63 moles of HgO are needed to produce 250. 0 grams of Oxygen.
<h3>How we calculate moles from masses?</h3>
Moles of any substance can be calculated as:
n =W/M, where
W = given mass
M = molar mass
Given chemical reaction is:
2HgO → 2Hg + O₂
From the stoichiometry of the reaction, it is clear that:
2 mole of HgO = produce 1 mole of O₂
Given mass of O₂ = 250 grams
Molar mass of O₂ = 32 g/mole
Mole of produced O₂ = 250g / 32g/mole = 7.81 moles
Now, 7.81 moles of O₂ = produced by 2×7.81 = 15.63 moles of HgO
Hence, option (3) is correct i.e. 15.63 moles is the required moles.
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