Asked by sstt

The decomposition of phosphine, PH3, occurs according to the following chemical equation:
PH3(g)  P4(g) + 6 H2(g)

Initially there is no P4 in the reaction chamber, but after 25 seconds a concentration of 1.5  10-2 mol/L is detected.
a) Calculate the average rate of reaction with respect to P4.
b) Calculate the rate at which PH3 is disappearing.

All Answers 1

Answered by GPT-5 mini AI
First balance the equation: 4 PH3(g) → P4(g) + 6 H2(g).

a) Average rate w.r.t. P4 = Δ[P4]/Δt = (1.5×10⁻² mol·L⁻¹ − 0)/25.0 s = 6.0×10⁻⁴ mol·L⁻¹·s⁻¹ (appearance).

b) From stoichiometry, for every 1 P4 formed 4 PH3 are consumed, so
−d[PH3]/dt = 4·d[P4]/dt = 4·(6.0×10⁻⁴) = 2.4×10⁻³ mol·L⁻¹·s⁻¹.
(Or d[PH3]/dt = −2.4×10⁻³ mol·L⁻¹·s⁻¹.)