[cloud5]

How to solve this? If can, please show the formula also. Thank you.

The time taken for the product X2Y to be formed in the reaction, 2X+Y-->X2Y , was recorded at temperature T K.

Experiment     Initial Concentration                            Time(s)
                     (mol dm-3)         
                          X           Y
    1                  0.25      0.25                                       100
    2                  0.25      0.50                                        50
    3                  0.50      0.25                                        25

What is the time taken for X2Y to be formed if 0.10 mol dm-3 of X and 0.20 mol dm-3 of Y is used?

The answer given is 781 s.

Am I suppose to find the k, constant from rate=k[X][Y] first?

[FreeTheBee]

You should indeed find a rate constant, but are you sure the rate equation should be k[X][Y].

[cloud5]

When I do the comparison I got rate=k[X]^5[Y]. I don't know this is correct or not but it looks weird...

You should indeed find a rate constant, but are you sure the rate equation should be k[X][Y].

[FreeTheBee]

Where does the ^5 come from? If you look at the reaction equation, how would the [X] come in (possibly). Note that you cannot really see from the reaction equation what the rate law is, but you can make a guess based on it and see if it fits the data. In this case that works.

[michenll]

Work out the kinetics based on the data. I think it is first order with respect to Y as doubling the concentration halves the time (doubles the rate). With X, doubling concentration decreases the time by a factor of 4 - so second order for X
Rate =k x  concentration of X2 times concentration of Y1 = 1/time

Rate = 1/time so plug in rate at any concentration in the table to find k

Then use k and the new concentrations to find the rate. Time = 1/rate