Question

The formula of phosphine gas is

• A. $\text{PH}_3$
• B. $\text{P}_2\text{H}_4$
• C. $\text{H}_3\text{PO}_3$
• D. $\text{H}_3\text{PO}_4$

Hint:

Remember the basic composition of common gases like phosphine, which can be crucial in identifying their correct chemical formulas.

Answer 1

The Correct Option is A

Step 1: What is phosphine.
Phosphine is a gas made only of phosphorus and hydrogen. We must pick its correct formula from the choices.
Step 2: Compare with ammonia.
Phosphorus sits just below nitrogen in the periodic table. Nitrogen forms ammonia $\text{NH}_3$, so phosphorus should form a similar hydride.
Step 3: Write the formula.
By the same pattern, phosphine is $\text{PH}_3$, with one phosphorus and three hydrogens.
Step 4: Rule out P2H4.
$\text{P}_2\text{H}_4$ is diphosphine, a different compound, not the simple phosphine gas.
Step 5: Rule out the acids.
$\text{H}_3\text{PO}_3$ and $\text{H}_3\text{PO}_4$ both contain oxygen. They are acids of phosphorus, not the hydride gas.
Step 6: Final choice.
So phosphine gas has the formula $\text{PH}_3$.\[ \boxed{\text{PH}_3} \]