weight of calcium 0.5g weight of water based on measured volume and accepted den
ID: 919501 • Letter: W
Question
weight of calcium 0.5g weight of water based on measured volume and accepted density 100g weight of reaction mix 100.5g initial temp of water to nearest 0.2 19.8 c final temp of the mix to neareset 0.2 28.8 difference in temp between -9 joules of heat evolved (show method of calculation)_________? write the net ionic eqution for the reaction of calcium with water____________? number of moles calcium used in the reaction___________? number of joules of heat evolved per mole of calcium_____________?
Explanation / Answer
Ca(s) +2H2O(l) -----> Ca(OH)2(aq) + H2 (g)
Net ionic : Ca(s) +2H2O(l) ----->Ca^+2(aq) + 2 OH^-(aq) + H2(g)
Amount of heat evolved (q) = m x s x deltaT
=> q = 100.5 x 4.184 x 9
=> q = 3784.4 J
Number moles of calcium used = mass / molar mass = 0.5 / 40 = 0.0125 mol
heat evolved per mole of calcium = -q / n = 3784.4 J / 0.0125 mol = -302.75 kJ/mol
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