Chem200 In-class activity Page 1 Thermodynamic Worksheet (20 points) Name: 1. If

Question

Chem200 In-class activity Page 1 Thermodynamic Worksheet (20 points) Name: 1. If you burn 22.0 g of propane (C3Hs) in a bomb calorimeter containing 3.25 L of water, what's the molar heat of combustion of propane if the water temperature rises 29.5 °C. Assume density of water is 1 g/ml. 2. What is the enthalpy change for the following reaction? N2(g) + 2 H2(g) NH4(1) Use the following: 112(g) + ½ O2(g) H2O(g) 11--242 kJ N2(g) + 2 H2O(g) N2H4(l) + O2(g) 11-534 k/ 3. The heat of reaction for the combustion of 1 mol of ethyl alcohol is-9.50 × 102 kJ. C2HsOH (I) + 3 O2 (g) 2 COz (g) + 3 H2O (l) How much heat is produced when 11.5 g of alcohol is burned? 4. Determine the heat of reaction (AHm) for the reaction, CaCO3 CO2 + CaO using the heat of formation given 1 l," (CaCO)--1207 kJ/mol, 11f"(CaO)--635 kJ/rmol, 1l," (CO2)--394 kJ/mol

Explanation / Answer

Q1

m = 22 g of propane

mol = mass/MW = 22/44 = 0.5

V = 3.25 L

mass = 3.25 kg= 3250 g

if dT = 29.5°C, find molar heat combustion

Qrxn = m*C*dT = 3250*4.184*29.5 = 401141 J

Qcombustion = -401141 / 0.5 = -802282 J/mol = -802.282 kJ/mol

Q2

HRxn is given by:

multiply rxn 1 by 2

2H2 + O2 = 2H2O H = -242*2 = -484

N2 + 2H2O = N2H4 + O2 H = 534

sum all

N2 + 2H2 = N2H4, which is what we need

add all

H = -484+534

H = 50 kJ

Q3

mol of alcohol = mass/MW = 11.5/46=0.25

1 mol of alcohol = -9.5*10^2

0.25 mol --> x

x = 0.25*9.5*10^2 = 237.5 kJ is produced

Q4.

HRxn = Hproducts- HRactants

HRxn = -394 + -635 - (-1207) = 178 kJ

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