Use the heat equation to calculate the energy, in joules, for each of the follow

Question

Use the heat equation to calculate the energy, in joules, for each of the following (see the table below): Table Specific Heats of Some Substances Substance Specific Heat (J/gC) Elements Aliminium, Al(s) 0.897 Copper, Cu(s) 0.385 Gold, Au(s) 0.129 Iron, Fe(s) 0.452 Silver, Ag(s) 0.235 Titanium, Ti(s) 0.523 Compounds Ammonia, NH3(g) 2.04 Ethanol, C2H5OH(l) 2.46 Sodium chloride, NaCl(s) 0.864 Water, H2O(l) 4.184 Water, H2O(s) 2.03

Part A

lost when 16.0 g of ethanol, C2H5OH, cools from 67.5 C to -45.0 C Express your answer using three significant figures.

Part 2

lost when 115 g of iron (Fe) cools from 117 C to 57 C Express your answer using two significant figures

Explanation / Answer

1. Ethanol boils at 78 deg.c. Hence ethanol at the given conditions is in the liquid form. Hence when cooled from 67.5 to -45 deg.c, it losses only sensible heat ( its freezing point is -114 deg.c)

Hence sensible heat given = mass* specific heat* temperature difference = 16*2.46*(67.5+45) =4428 joules

2. for iron also melts at 1538 deg,c and boils at 2861 deg.c. for the given conditions, iron losses only sensible heat which is = 115*0.452*(117-57)=3119 joules

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