How do I write the chemical equations to the following descriptions (the answers are already known, I just need instructions on how to reach them):
a) 3 atoms of carbon combine with 4 molecules of hydrogen to produce methane (CH4)
b) 7 molecules of hydrogen and 2 molecules of nitrogen gases react to produce ammonia
c) 4 molecules of hydrogen and 5 molecules of chlorine react [ans: H2 +Cl2---> 2HCl]