The frozen balloon shrank because the average kinetic energy of the gas molecules in a balloon decreases when the temperature decreases. This makes the molecules move more slowly and have less frequent and weaker collisions with the inside wall of the balloon, which causes the balloon to shrink a little.
23.67 g unless you're rounding to significant figures than it's 24 g
No. It's a phase change, and all phase changes are physical
First, write out a complete balanced reaction for the combustion of ethane, ethane + O2 -> CO2 + H20. Then, divide the grams of ethane by its Molar Mass and multiply by 32, the molar mass of O2.