How many grams of o2(g) are needed to completely burn 73.7 g of c3h8(g)?

Which diagram shows the correct way to represent an ionic compound of magnesium oxide?

3. how much energy in joules is required to evaporate .0005 kg of liquid ammonia to vapor at the same temperature? 4. how much energy ( in megajoules ) is given up by .75 kg of water at 0c when it freezes to form ice at 0c? 5. explain how heat works between and at critical temperatures?

Can someone me with 3 and 4 plz. this is for masteries test.