Calculate the mass of 4.50 moles of Ca3 (PO3) 4

Stoichiometry:

First, calculate the number of grams for one mole of Ca3 (PO3) 4

(3 * (Mass of Ca)) + (4 * (Mass of P + (3 * Mass of Oxygen)))

= (3*40.08) + 4 (30.97 + (3*16.00))

= (120.24) + 4 (78.97)

=436.12 g / mol Ca3 (PO3) 4

This means there are 436.12 g per 1 mole of Ca (PO3) 4. Since there are 4.50 moles of Calcium Phosphate, mulitply the molar mass of Ca (PO3) 4 by 4.50 and you should get 1962.54 g. Since there are 3 sigfigs, the final answer is 1960 g.

on a side note: I put in all my work in case 1. your periodic table if different, 2. my work is wrong, 3. you put in the question wrong because I feel that the actual compound would be Ca3 (PO4) 3 instead of Ca3 (PO3) 4 (if this is the case, the answer should be 1820 g).