Practical assessment of STPM Chemistry

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Experiment 6 (Thermochemistry)

Purpose: to determine the hear of neutralisation of a strong acid with a strong base

Questions: c) heat released of each of the experiment, q = m x c x change of T = (10 + 30) x 4.2 x change of T

d) no. of moles of sollutions can be found by n = MV/1000

e) Ionic equations: H+ + OH- --H2O

f) Heat of neutralisation: H = c)/ d)

g) acid W is a diprotic acid h) - Mixture of solution must be sitrred through out the exp. - solutions must be mixed quickly to attain the maximum change of temperature.

Experiment 12 Question Answer provided served as reference,

e) From the graph of EO against lg [Zn2+], the value of Eo increases as the value of lg [Zn2+] decreases. Therefore the e.m.f. of the cell increases when the concentration of Zn2+ ions decreases.

f) (i) with reference of Nernst Equation, 0.059 [Zn2+] Ecell = EØcell + n lg [Cu2+] The value of lg [Zn2+]/[Cu2+] increases when the concentration of Cu2+ ions decreases. Hence the e.m.f. value decreases with the decrease in Cu2+ ions.

(ii) The Eo value for Al is larger than the Eocell value for zinc. Hence with the reference to the Nernst Equation, the Eocell value will be larger/