12.4 g of phosphorus reacts with 9.6 g of oxygen. Which of the following chemical equation represents this reaction?
[Relative atomic mass: P, 31; 0, 16]
A P + O2 + PO2
B 2 P + O2 + 2 PO
C 3P +2 02 → P304
D 4P +3 02 → 2 P203

D 4P +3O₂ → 2 P₂O₃

Explanation:

In this problem, we need to convert the mass of phosphorus and oxygen to moles trying to find the ratio of reaction (The moles of P that reacts per mole of O₂):

Moles P:

12.4g P * (1mol P / 31g) = 0.4 moles

Moles O₂:

9.6g * (1mol / 32g) = 0.3 moles

The ratio of reaction is:

0.4 mol / 0.3 mol = 1.33 = 4 moles of P / 3 moles of O₂

That means 4 moles of P react with 3 moles of O₂ and the reaction that represents this ratio is:

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g