What mass of osmium (in grams) contains the same number of atoms as 8.62 grams of selenium?

What is the density of the black hole

1. combine iron and copper (ii) sulfate solution. (hint: iron will form the iron (iii) ion) fe + cuso4 → 2. combine lead (ii) nitrate and potassium iodide solutions. pb(no3)2+ kl → 3. combine magnesium metal and hydrochloric acid solution. mg + hcl → 4. electrolysis (splitting) of water. h2o → 5. burning magnesium. mg + o2 →

What mass of natural gas (ch4) must you burn to emit 276 kj of heat?