Question

Calculate the energy change (with the correct sign) when the temperature of 100.0 mL of liquid water increases by 4.40 °C.

Calculate the mass of NaO2CCH3 needed to release this amount of energy when dissolved in water. ΔHsolution(NaO2CCH3) = -989.5 J/mol.

Answer 1

specific heat capacity of water, C = 4.186 J/goC
density of water = 1 g/mL
Volume = 100 mL
Mass of water = density * volume = 1 * 100 = 100 g

Q = m*C*(Tf-Ti)
     = 100*4.186*(4.4)
    =1842 J
Answer: 1842 J
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delta H solution = -989.5 J/mol
number of moles of NaO2CCH3 required = 1842 J / 989.5 J/mol = 1.86 mol
Molar mass of NaO2CCH3 =23 + 2*16 + 2*12 + 3*1= 82 g/mol
mass of NaO2CCH3 = number of moles * molar mass
                                        = 1.86 mol * 82 g/mol
                                        = 152.5 g
Answer: 152.5 g