05-09-2018, 03:43 PM

I just want to confirm if I have got the answers right to some revision questions for chemistry. Would be very grateful if someone can give productive input to what I post. Thank You

The question is:

Q5. In a particular reaction, the order of reaction with respect to compound C is known to be fractional. The rates of reaction were measured for different concentrations of C (all other reagents were present in large excess). What is the order of reaction with respect to C?

[C]/M 0.842 0.739 0.644 0.557 0.476 0.401

rate/M s^-1 1.40 1.36 1.33 1.29 1.25 1.21

The answer is ONE of the following: 1/5, ¼, 1/3, ½, 2/3, ¾, 5/4, 4/3, 3/2.

To work out the fractional order of reaction I used the “Initial rate method” by applying the following formula:

ln (rate) = aln[A] + ln(k)

y = m x + c

I read in a book that “So if we know the rate at different [A] we can plot ln (rate) vs ln [A], the gradient will be a, the order of the reaction”.

So I produced the following table from the table above:

ln(A) -0.17198 -0.30246 -0.44006 -0.58519 -0.74234 -0.91379

ln(rate) 0.336472 0.307485 0.285179 0.254642 0.223144 0.19062

So based of this I made a graph (image attached) in excel and the equation produced was:

y = 0.1957x + 0.3692

The gradient is m so I used 0.1957, but I know excel isn’t accurate when predicating the gradient as its better to do it physically using graph paper. So I just rounded 0.1957 to 0.2 and choose the fractional order 1/5.

Is this right? Have I made a mistake anywhere?

Thanks

The question is:

Q5. In a particular reaction, the order of reaction with respect to compound C is known to be fractional. The rates of reaction were measured for different concentrations of C (all other reagents were present in large excess). What is the order of reaction with respect to C?

[C]/M 0.842 0.739 0.644 0.557 0.476 0.401

rate/M s^-1 1.40 1.36 1.33 1.29 1.25 1.21

The answer is ONE of the following: 1/5, ¼, 1/3, ½, 2/3, ¾, 5/4, 4/3, 3/2.

To work out the fractional order of reaction I used the “Initial rate method” by applying the following formula:

ln (rate) = aln[A] + ln(k)

y = m x + c

I read in a book that “So if we know the rate at different [A] we can plot ln (rate) vs ln [A], the gradient will be a, the order of the reaction”.

So I produced the following table from the table above:

ln(A) -0.17198 -0.30246 -0.44006 -0.58519 -0.74234 -0.91379

ln(rate) 0.336472 0.307485 0.285179 0.254642 0.223144 0.19062

So based of this I made a graph (image attached) in excel and the equation produced was:

y = 0.1957x + 0.3692

The gradient is m so I used 0.1957, but I know excel isn’t accurate when predicating the gradient as its better to do it physically using graph paper. So I just rounded 0.1957 to 0.2 and choose the fractional order 1/5.

Is this right? Have I made a mistake anywhere?

Thanks