Question

Use the heat equation to calculate the energy, in joules and calories, for each of the following (see the table):

Specific Heats for Some Substances
Substance	cal/g ∘Ccal/g ∘C	J/g ∘CJ/g ∘C
Elements
Aluminum, Al(s)Al(s)	0.214	0.897
Copper, Cu(s)Cu(s)	0.0920	0.385
Gold, Au(s)Au(s)	0.0308	0.129
Iron, Fe(s)Fe(s)	0.108	0.452
Silver, Ag(s)Ag(s)	0.0562	0.235
Titanium, Ti(s)Ti(s)	0.125	0.523
Compounds
Ammonia, NH3(s)NH3(s)	0.488	2.04
Ethanol, C2H6O(s)C2H6O(s)	0.588	2.46
Sodium chloride, NaCl(s)NaCl(s)	0.207	0.864
Water, H2O(s)H2O(s)	1.00	4.184
Water, H2O(s)H2O(s)	0.485	2.03

a.) to heat 28.3 gg of water from 12.5∘C∘C to 29.7 ∘C-- answer in J and Cal

b.) to heat 40.0 gg of copper from 122∘C∘C to 253 ∘C - answer in J and Cal

c.) lost when 13.9 g of ethanol, C2H5OHC2H5OH, cools from 64.0 C to -42.0∘C- answer in J and Cal

d.)lost when 115 g of iron cools from 118∘C∘C to 54 ∘C- answer in J and Cal

Answer 1

a)

mass of water = 28.3 g

temperature difference = 29.7 - 12.5 = 17.2 oC

Q = m Cp dT

   = 28.3 x 4.184 x 17.2

   = 2036.6 J

heat energy = 2037 J

                    = 487 cal

                   = 0.487 Cal

b)

mass of copper = 40.0 g

Q = m Cp dT

   = 40 x 0.385 x (253 - 122)

Q = 2017 J

heat energy = 2017 J

                    = 482 cal

C)

Q = 13.9 x 2.46 x (-42 - 64)

= 3625 J

   = 866 cal

d)

Q = 115 x 0.452 x (54-118)

   = 3327 J

= 795 cal