3.(4 points) find the mass percent composition of all elements in ammonium phosphate.

Explanation:

Step1: Write the chemical formula

The chemical formula of ammonium phosphate is $(NH_4)_3PO_4$.

Step2: Determine atomic masses

Atomic mass of N: $14.01\ g/mol$, H: $1.01\ g/mol$, P: $30.97\ g/mol$, O: $16.00\ g/mol$.

Step3: Calculate molar - mass of $(NH_4)_3PO_4$

$n_N = 3\times1 = 3$, $n_H=3\times4 = 12$, $n_P = 1$, $n_O = 4$ $M=(3\times14.01)+(12\times1.01)+30.97+(4\times16.00)$ $M = 42.03+12.12 + 30.97+64.00=149.12\ g/mol$

Step4: Calculate mass - percent of each element

Nitrogen

Mass - percent of N: $\frac{3\times14.01}{149.12}\times100%=\frac{42.03}{149.12}\times100%\approx28.19%$

Hydrogen

Mass - percent of H: $\frac{12\times1.01}{149.12}\times100%=\frac{12.12}{149.12}\times100%\approx8.13%$

Phosphorus

Mass - percent of P: $\frac{30.97}{149.12}\times100%\approx20.77%$

Oxygen

Mass - percent of O: $\frac{4\times16.00}{149.12}\times100%=\frac{64.00}{149.12}\times100%\approx42.92%$

Answer:

Nitrogen: approximately $28.19%$, Hydrogen: approximately $8.13%$, Phosphorus: approximately $20.77%$, Oxygen: approximately $42.92%$