Consider the general reaction: 2 A + b B → c C and the following average rate data over a specific time period \Delta t: - \frac{ \Delta A}{\Delta t} = 0.0080 mol L-1 s-1 - \frac{ \Delta B}{\Delta t} = 0.0120 mol L-1 s-1 \frac{ \Delta C}{\Delta t} = 0.0160 mol L-1 s-1 Determine what the coefficient c could be in the balanced equation. Select one: 1 5 2 3 4

c = 4

Explanation:

In general, for the reaction

       a A     +    b B     ⇒ c C   +    d D

the rate is given by:

rate = - 1/a ΔA/Δt = - 1/b ΔB/Δt = + 1/c ΔC/Δt = + 1/d ΔD/Δt

this is done so as to express the rate in a standarized way which is the same to all the reactants and products irrespective of their stoichiometric coefficients.

For this question in particular we know the coefficient of A and need to determine the coefficient c.

- 1/2 ΔA/Δt = + 1/c ΔC/Δt

- 1/2 (-0.0080 ) = + 1/c ( 0.0160 mol L⁻¹s⁻¹ )

0.0040 mol L⁻¹s⁻¹  c = 0.0160 mol L⁻¹s⁻¹

∴ c = 0.0160 / 0.0040 = 4

the answer for sodium is 0.186

the answer for rubidium is 0.251