Question

Need help on 5 and 6

Phosphoric acid, H_3PO_4, has some important applications. It can be used to produce fertilizers and it is present in cola drinks. Phosphoric acid can be made from phosphorus in a two-step process: Reaction 1: P_4 + 5 O_2 --- rightarrow P_4O_10 Reaction 2: P_4O_10 + 6 H_2O rightarrow 4 H_3PO_4 What is the molar mass of phosphoric acid, H_3PO_4? How many moles of phosphoric acid can be produced from 1 mole of P_4? A synthesis yielded 114 g of phosphoric acid. How many moles of phosphoric acid were produced? How many moles of P_4 would be required to produce the moles of phosphoric acid determined in question 3? Convert the moles of P_4 determined in question 4 into grams (which tells us the grams of P_4 that actually reacted). Let's say that the experimentalist actually used 175 g taken from a bottle labeled P_4. Based upon your answer to question 5 you can see that it did not all react. We will assume this was because the reagent in this bottle contained inert impurities, based upon your answer to question 5 and the grams of chemical taken from the reagent bottle, what was the actual mass percent P_4 in the bottle?

Answer 1

1) molar mass of H3PO4 is 98g/mol

2) From one mole of P4 , 4 moles of H3PO4 can be obtained as per the stoichiometric equation

3) yield = 114 g

= 114/98

=1.1632 mol

4) According to the equations

1 mole of P4 produces 4 moles of H3PO4

moles of P4 that can produce 1.1632 moles of H3PO4 is

= 1.1632 x 1/4=

= 0.29 moles of P4

5) mass of P4 used in question 4 = 0.29 x 124

= 35.96 g

6) Out of 175 g taken from bottle of P4 only 35.96 g are P4 that reacted

mass percent of posphorus= mass of P4x100/mass of sample

= 35.96x100/175

= 20.55%