Could someone me with answer 3 and 5 , you so much

The covalent compound acetylene, which is the fuel of the oxyacetylene torch used by welders, has the molecular formula c2h2. the covalent compound benzene, a commercial solvent, has the molecular formula c6h6 each of these covalent compounds contains carbon and hydrogen atoms in a one-to-one ratio. would it be correct to write the chemical formulas of each as ch? explain.

Name the element in group 17, period 2. (periodic table)

650.j is the same amount of energy as? 2720cal1550cal650.cal2.72cal