Ammonia react with phosphorus acid to form a compound that contains 28.2% of nitrogen 20.8%, phosphorus 8.1% of hydrogen 42.9%oxygen. calculate the empirical formula of this compound

Empirical formula will be (NH₄)₃PO₄, which matches the molecular formula

Explanation:

This is the reaction:

NH₃ + H₃PO₄ → 28.2% N, 20.8% P, 8.1% H, 42.9% O

In 100 g of compound we have:

28.2 g N

20.8 g of P

8.1 g of H

42.9 g of O

Now we divide each  between the molar mass:

28.2 g / 14 g/mol = 2.01 mol

20.8 g / 30.97 g/mol = 0.671 mol

8.1 g / 1 g/mol = 8.1 mol

42.9 g / 16 g/mol =  2.68 mol

And we divide again between the lowest value of moles

2.01 mol / 0.671 mol → 3

0.671 mol / 0.671 mol → 1

8.1 mol / 0.671 mol → 12

2.68 mol / 0.671 mol → 4

Molecular formula will be: N₃PH₁₂O₄ → (NH₄)₃PO₄

Empirical formula will be (NH₄)₃PO₄, which matches the molecular formula

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.