Problem: When backpacking in the wilderness, hikers often boil water to sterilize it for drinking. Suppose that you are planning a backpacking trip and will need to boil 36 L of water for your group. What volume of fuel should you bring? Assume each of the following: the fuel has an average formula of C7H16; 15% of the heat generated from combustion goes to heat the water (the rest is lost to the surroundings); the density of the fuel is 0.78 g/mL; the initial temperature of the water is 25.0 oC; and the standard enthalpy of formation of C7H16 is –224.4 kJ/mol.

🤓 Based on our data, we think this question is relevant for Professor Fokwa's class at UCR.

FREE Expert Solution

We are asked to calculate the volume of fuel you should bring.


Calculate heat of combustion fo fuel: 

C7H16(g) + 11 O2(g) → 7 CO2(g) + 8 H2O(g)


ΔH°rxn=ΔH°f, prod-ΔH°f, react


Note that we need to multiply each ΔH˚f by the stoichiometric coefficient since ΔH˚f is in kJ/mol. 

Also, note that ΔH˚f for elements in their standard state is 0.


ΔH°rxn=ΔH°f, prod-ΔH°f, reactΔH°rxn=(7(-393.51 kJ)+8(-241.82 kJ))-((224.4 kJ)+11(0 kJ))

ΔH°rxn = -4464.73 kJ 


Calculate heat needed to boil per g: 

q1 =CT=(4.184 J/g°C)(100°C-25°C) = 313.8 Jq2 =Hvap=2260 J/g qtotal = 2573.8  J/g


View Complete Written Solution
Problem Details

When backpacking in the wilderness, hikers often boil water to sterilize it for drinking. Suppose that you are planning a backpacking trip and will need to boil 36 L of water for your group. What volume of fuel should you bring? Assume each of the following: the fuel has an average formula of C7H16; 15% of the heat generated from combustion goes to heat the water (the rest is lost to the surroundings); the density of the fuel is 0.78 g/mL; the initial temperature of the water is 25.0 oC; and the standard enthalpy of formation of C7H16 is –224.4 kJ/mol.

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Enthalpy of Formation concept. You can view video lessons to learn Enthalpy of Formation. Or if you need more Enthalpy of Formation practice, you can also practice Enthalpy of Formation practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Fokwa's class at UCR.