Yes you can BUT because you asked this question you should have a
pro show you how to do it. Just to give you a worst case example,
transformers work in both directions so if you feed the "city" with
220v your neighbors will enjoy your power until your generator
burns up. Maybe 2-3 seconds!
Yes, IF you have a neutral connection at your generator. If you do
not connect the neutral you will not have 110v from hot to neutral.
This is because your house must be perfectly balanced across the
neutral to have the correct voltage divider to split 220V into
110V. This is near impossible in a residential situation. You need
the neutral for 110V.
Also, buy a generator transfer panel if you plan to power your
house off a generator. It's the law.
Not because it's the law, but if you don't have a transfer panel
and you connect it directly to your panel you'll also be putting
current to the lines coming into your house.
This is real scary for the electricians that come out to repair
the power. The (city) power is off and they don't expect to see
(feel!) any on your end. You could end up electrocuting