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Unformatted text preview: H2O = -1726J q endo = -q exo = +1726kJ xmoles NH 4 NO 3 = 20g NH 4 NO 3 * 1mol/80g = 0.25 moles NH 4 NO 3 q endo = +1726kJ/0.25mol NH 4 NO 3 = 6900 J/mol NH 4 NO 3 4. Three metal blocks (Cu(s), Pb(s), Al(s)), each of mass 827g, of temp. 82.6C, are added separately to 600Ml H 2 O(l) at 20.0C in each of three beakers. (a) calculate specific heat capacity of Cu(s) if final experimental temp. is 26.6C. (a) q exo = q Cu(s) = (x * J/g-C)(827g)(26.6C 82.6C) q exo = -46312x q endo = q cold H2O = (4.164 J/g-C)(600g)(26.6C-20.0) q endo = -q exo solve for x = x = C Cu(s) = .357 J/g-C (b) Given that C Pb(s) = 0.128 J/g-C, calculate final temp. (t f ) (b) q exo = q Pb(s) = (0.128 J/g-C)(827g)(t f 82.6C) q endo = q cold H2O = (4.184 J/g-C)(600g)(t f -20.0) solve for t f , t f = 22.5C (c) State basic assumption in working three problems. (c) C Cu(s) = .385 J/g-C C Al(s) = .90 J/g-C C Pb(s) = .128 J/g-C C H2O(l) = 4.184 J/g-C...
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