I haven't done A level chemistry for over 5 years. From memory and some reasonable knowledge of the equilibrium constants, i worked out the answer for question 8 as Exothermic and the temperature increasing. Not sure if i am entirely correct?
I do not have an idea how to start about answering question 9.
Kc increases with temperature. Kc = [products]/[reactants]. Increasing Kc means more products than before, i.e. equilibrium -> RHS. Therefore endothermic. Q9: I'd go with Ka = [H+] x [A-]/[HA]. When you add half the volume of OH- needed to fully neutralise (i.e. the volume that makes the graph go vertical) then [A-] = [HA], so Ka = [H+] and pKa = pH = 5.
I think i have figured out the Ka value and i have got it as B (5 ka). Am i correct?
Yes, pKa=pH at the half-equivalence point. Since the equivalence point is 30cm3, the half-equivalence point is 15cm3 which corresponds to pH=5 so pKa=5. Thus
Question 8, i think i have made a mistake and the answer should be in fact be D (Increases and it should be endothermic as Kc has increased due to the temperature being increased)?
That is from what i have read. Is this correct also?
So as the value of Kc has increased when the temperature has increased, it means the [NO] has increased in relation to the [N2] and [O2]. Therefore, the forward reaction has to be endothermic so equilibrium would shift to the right to oppose the increase the temperature thus increasing the concentration of NO.
So as the value of Kc has increased when the temperature has increased, it means the [NO] has increased in relation to the [N2] and [O2]. Therefore, the forward reaction has to be endothermic so equilibrium would shift to the right to oppose the increase the temperature thus increasing the concentration of NO.
Yeah. Thanks again. I think i should have done a chemistry degree rather than a physics related one as i had more intrigue in the last day working these out than any of my physics topics.