Four-part question set: A chemist dissolves 30.0 g of potassium phosphate in one

Question

Four-part question set: A chemist dissolves 30.0 g of potassium phosphate in one beaker of water and 30.0 g of silver() nitrate in a second beaker of water. When the two solutions are poured together, a solid precipitate forms. Write a balanced molecular equation, determine the identity of the limiting reactant, and predict the expected mass of solid product. (Ignore equilibrium.) 28. What is the identity of the solid product? 29. Add together all the coefficients in the balanced equation. What is the total? 30. What is the identity of the limiting reactant? 31. What is the predicted mass of the solid product? 28. 29. 30. 31.

Explanation / Answer

28.

Balanced equation is,

K3PO4 (aq.) + 3 AgNO3 (aq.) -------> Ag3PO4 (s) + 3 KNO3 (aq.)

The precipitate is = Ag3PO4, Silver phosphate

29.

Total of coefficients = 1 + 3 + 1 + 3 = 8

30.

Moles of K3PO4 = mass / molar mass = 30.0 / 212.3 = 0.141 mol

Moles of AgNO3 = 30.0 / 169.9 = 0.176 mol

From the balanced equation,

1 mol of K3PO4 needs 3 mol of AgNO3.

Hence, AgNO3 is limiting reagent.

31.

3 mol of AgNO3 gives 1 mol of Ag3PO4

then,

0.176 mol of AgNO3 gives 0.176 * 1 / 3 = 0.0588 mol of Ag3PO4

Therefore, Mass of product = moles * molar mass = 0.0588 * 418.6 = 24.6 g.

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