Quartz, sio2, is the most common mineral found on the surface of the earth. what is the best explanation for the fact that quartz is hard and has a high melting point as opposed to other oxides like no2 and co2?

Hydrogenation reactions, in which h2 and an "unsaturated" organic compound combine, are used in the food, fuel, and polymer industries. in the simplest case, ethene (c2h4) and h2 form ethane (c2h6). if 140 kj is given off per mole of c2h4 reacting, how much heat (in mj) is released when 12 kg of c2h6 forms?