Answer to Question #56220 in General Chemistry for Yehan

Question

Jane wants to make an acid. She has two possible compounds she could add to 250.0 g of water to
make this acid – EITHER 234.5 g of calcium oxide OR 678.9 g of tetraphosphorus decaoxide (she won’t use both, just one).
a. Which compound should she use? Explain your answer (with words and full sentences), and write any balanced chemical reactions that would help you justify your claim.

b.
What is the chemical formula of the acid, and what is the maximum mass of the acid she could
theoretically produce when she does this reaction?

c. What is the EXCESS reactant, and how many grams of this reactant are leftover when the reaction is
completed?

Answer 1

a. Calcium oxide is a basic oxide. Soluble in water, releasing energy, forming calcium hydroxide:
СаО + Н₂О → Са(ОН)₂
Thus, this material is not suitable for producing acid.
P₄O₁₀ actively reacts with water to produce phosphoric acid:
P₄O₁₀ + 6 H₂O → 4 H₃PO₄

b. Molar mass P₄O₁₀ is 283.9 g/mol
The 678.9 g P₄O₁₀ contains 678.9 / 283.9 = 2.39 mol P₄O₁₀
The molar mass of Н₂О is 18.0 g / mol
The 250.0 g of Н₂О contains 250.0 / 18.0 = 13.89 mol Н₂О
In accordance with the reaction equation, 1 mol P₄O₁₀ reacted with 6 moles of water.
Then, to turn into acid 2.39 mol Р4O10 need 2.39 * 6 = 14.34 mol of water. Jane has 13.89 mol of water..
13.89 mol Н₂О react to 13.89 / 6 = 2.315 mol P₄O₁₀.
From 2,315 mol P₄O₁₀ produced 2,315 * 4 = 9.26 mol of H₃PO₄
The molar mass of H₃PO₄ equal to 98.0 g / mol Then the mass of the resulting phosphoric acid is 9.26 * 98.0 = 907.5 g

c. Excess P₄O₁₀ is 2.39 - 2.315 = 0.075 mol.
Mass excess P₄O₁₀ is 0.075 * 283.9 = 21.3g