Acetylene (C2H2) and a hydroxide can be made by reacting calcium carbide (CaC2)
ID: 613601 • Letter: A
Question
Acetylene (C2H2) and a hydroxide can be made by reacting calcium carbide (CaC2) with water. a) write a balanced equation for the reaction. b) what is the maximum amount of heat (in joules) that can be obtained from the combustion of acetylene, starting with 61.4g CaC2? delta H f (CO2) = - 393.5 kJ/mol delta H f (C2H2) = 226.6 kJ/mol delta H f (H2O) = -285.8 kJ/molExplanation / Answer
1/ If you want a scientific explanation for this, you should first be aware that combustion is actually red-ox reaction between acetylene, reducing agent and Oxygen, oxidizing agent. As Oxygen is a very strong oxidizing chemical, the reaction only completes when acetylene is completely oxidized, meaning the oxidation state of all the reducing elements in acetylene (H, C) is maximum (for the reducing agent always has its oxidation state increase in red-ox reaction as it gives electrons, the negative charge away). (Additional explanation, not really important) For H, the highest oxidation state is +1 in H2O (it can also be -1 in NaH, or 0 in CH4). Similarly, C will have the highest oxidation state, which is +4 in CO2. (in CO, it only has +2 ox. st.). O is an oxidizing agent so it has oxidation state -2. Thus, the final products of such combustion is CO2 and H2O, for the reducing elements have the highest possible oxidation states in these compounds. 2/ Stoichiometric equation of the chemical combustion: C2H4 + 3 O2 -> 2 CO2 + 2 H2O So the ratio is 1:3. That's how I interpret you question, but if it's like that, the information about 20% oxygen in the air is really irrelevant.