A chemistry graduate student is studying the rate of this reaction: NH4OH(aq)→NH3(aq)+H2O(aq)

She fills a reaction vessel with and measures its concentration as the reaction proceeds:

Time (minutes) NH4OH
0 0.200M
1.0 0.0895M
2.0 0.577M
3.0 0.0426M
4.0 0.0337M

Use this data to answer the following questions.

a. Write the rate law for this reaction.
b. Calculate the value of the rate constant.

Rate = k[NH₄OH]²

k = 6.17

Explanation:

We have concentrations of NH₄OH along with the given times. To determine the rate law of the reaction we need to determine first the order of reaction. This reaction can be order zero, first or second order. The expressions for each are the following:

Zero order:

k = [A₀] - [A] / t

First order:

k = 1/t * ln([A₀]/[A])

Second order:

k = (1/t) * (1/[A₀] - 1/[A])

And from here, the next part is easier. We just need to determine hat order is, calculating the value of k at two different times. If the value of k is constant, then we can say that the reaction is of that order.

Let's suppose its order zero (t = 1 and t = 2, [A₀] = 0.200 M):

k1 = 0.2 - 0.0895 / 1 = 0.1105

k2 = 0.2 - 0.577 / 2 = -0.1885

From this results we can conclude it's not zero order.

Let's suppose its order 1:

k1 = ln(0.2/0.0895) / 1 = 0.8041

k2 = ln(0.2/0.577) / 2 = 0.1733

It's not first order either, so we can conclude that this reaction is of 2nd order and the rate law would be:

Now that we know it's a second order reaction, we can determine the value of k using its expression:

k = (1/t) (1/[A] - 1/[A₀])

k = ln(1/0.0895 - 1/0.2) (1/1)

k = 6.17

And to confirm this value, let's calculate k for t = 2 s

k = (1/2) (1/0.0577 - 1/0.2)

The value is constant, so this is the true value of k.

Hope this helps

what are the choices?

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-