stuck on rate equation question

pls can someone explain why B is 2nd order? I thought it was 0?

i found that A is 1st order, so for B i looked at experiment 2 and 3, i looked at the effect A also had on the rate since both A and B were changing, i found the new rate with A was 1.8x10-5 when i did 0.90x2 because A is first order? then i divided this new rate by the rate they have given in experiment 3= 7.20x10-5 and i got 2.5x10-11, so i assumed this meant B is 0 order? is my working out wrong? pls can somoene show me how im supposed to do this

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ive posted it, sorry took me a while

thank u

mathematical method above

logic method
from 2 to 3
[A] doubled
this causes rate to double
but in fact rate in 3 is x8 the rate in 2
so change in concentration of B caused rate to x4 (quadruple)
doubling in concentration of B causes rate to x4
so order wrt B is 2nd order

thank u! i prefer this method, once i know that 0.90x10-5 x 2cubed = 7.20x10-2, how does this mean B is x4? is it because A is x2 so u do 8/2 = 4

yes
rate changes only due to change in concentration
both concentration of A and B changed

we know from 2 to 3 rate x8
from 2 to 3, [A] doubled. order wrt A is first order. so doubling [A] doubled rate
overall change in rate is x8
since we know change in [A] caused rate to double, other changes in rate must be due to
so change in concentration of B caused rate to x4

change in [A] -> x2
change in -> x4
overall -> x8

hence doubling quadruples rate
so order wrt B is 2nd order

yes
rate changes only due to change in concentration
both concentration of A and B changed

we know from 2 to 3 rate x8
from 2 to 3, [A] doubled. order wrt A is first order. so doubling [A] doubled rate
overall change in rate is x8
since we know change in [A] caused rate to double, other changes in rate must be due to
so change in concentration of B caused rate to x4

change in [A] -> x2
change in -> x4
overall -> x8

hence doubling quadruples rate
so order wrt B is 2nd order

can i use this same method for finding order of F in another question? once i found E is 2nd order, from exp 1 to 2, u x9 for rate, and to work out F using exp 2 and 3, E is also changing there, u x2 from exp2 to 3 so the effect on the rate in exp 2 would be 3.78x10-3 x4? and to work effect of F its 3.78x10-3 x2= 7.56x10-3. how does this mean F is 1st order? do i do 9/4= 2.25

Yes method always works

from 2 to 3,
conc of E doubled, rate should x4
in fact, rate x 2
other changes in rate is due to change in conc of F
so change in conc of F caused rate to halve

[E] x 2 -> rate x 4 (2nd order)
[F] x 1/2 -> rate x 1/2
overall -> rate x 2

so halving [F] caused rate to 1/2
hence first order wrt F