Upon complete combustion, the indicated substances eveolve the given quantities of heat. Write a balanced equation for the combustion of 1.00 mol of each substance, including the enthalpy change, ÄH, for the reaction.
a) 0.548g of propane, C3H8(g), yields 29.4 J
b) 2.35 mL of acetone, (CH3)2CO(l) (d=0.791 g/mL), yields 58.3J
This is just a practice homework question, can someone please just get me started on one, and I can probably do the rest.
C3H8 + 5O2 ==> 3CO2 + 4H2O
0.548 g C3H3 is 0.548/approximately 44 (you need to calculate it exactly) = about 0.01245 mols. So you had 0.1245 mol that evolved 29.4 J. Delta H is the amount evolved for 1.00 mol so
29.4 J/0.01245 mol = about 2360 J/mol.
To write a balanced equation for the combustion of a substance, you need to know the reactant and the products involved in the reaction. In this case, we are given the mass of the substance, the quantity of heat evolved, and the molar mass of the substance.
Let's start with part (a) where we are given 0.548g of propane (C3H8(g)) and it yields 29.4 J of heat. To write a balanced equation, we need to determine the reactants and products.
1. Calculate the number of moles of propane:
- Given mass of propane = 0.548 g
- Molar mass of propane (C3H8) = (3 * atomic mass of carbon) + (8 * atomic mass of hydrogen)
= (3 * 12.01 g/mol) + (8 * 1.01 g/mol)
= 44.11 g/mol
- Moles of propane = (mass of propane) / (molar mass of propane)
= 0.548 g / 44.11 g/mol
= 0.0124 mol (approximately)
2. Write the balanced equation for the combustion of propane:
C3H8(g) + O2(g) → CO2(g) + H2O(g)
3. Determine the enthalpy change (ΔH) for the reaction:
- Given quantity of heat (q) = 29.4 J
- Moles of propane = 0.0124 mol
- Enthalpy change per mole of propane = (quantity of heat) / (moles of propane)
= 29.4 J / 0.0124 mol
≈ 2371 J/mol (approximately)
Therefore, the balanced equation for the combustion of 1.00 mol of propane (C3H8(g)), including the enthalpy change, ΔH, is:
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) ΔH = -2371 J
Now, you can use a similar approach to solve part (b) for the combustion of acetone [(CH3)2CO(l)]. Remember to convert mL to grams using the density of acetone.