#### Question

A first order reaction has a rate constant 1.15 10^{−3} s^{−1}. How long will 5 g of this reactant take to reduce to 3 g?

#### Solution

From the question, we can write down the following information:

Initial amount = 5 g

Final concentration = 3 g

Rate constant = 1.15 10^{−3} s^{−1}

We know that for a 1^{st} order reaction,

`t = 2.303/k log""([R]_0)/[R]`

= `2.303/(1.15xx10^(-3))log 5/3`

= `2.303/(1.15xx10^(-3)xx0.2219`

= 444.38 s

= 444 s (approx)

Is there an error in this question or solution?

Solution A first order reaction has a rate constant 1.15 10-3 s-1. How long will 5g of this reactant take to reduce to 3g? Concept: Factors Influencing Rate of a Reaction.