If I drink 1 12oz beer at 11% is that equal to drinking 2 12oz beers at 5.5%.
I'm assuming by "equal" you are referring to the drunk/buzz potential. If so, this effect depends on the concentration of alcohol in your brain. And that involves 2 factors:
1. The first and most obvious is the amount of alcohol you ingest. In that sense, yes 12 oz of 11% alcohol is equal to 24 oz of 5.5% alcohol.
2. But the other factor is how quickly the alcohol gets into your brain. Think about it -- if you drink 3 beers in 30 minutes you are going to feel more effect then if you drink 3 beers over 3 days. You've ingested the same amount of alcohol but the concentration in your brain is much higher in the first case then in the second.
The two main factors that dictate how fast the alcohol gets from your glass to the brain are (a) how fast you drink it; and (b) how fast your stomach empties into your intestines (gastric emptying time). That's because the alcohol gets absorbed into your blood from your intestines, not your stomach. If your stomach empties quickly, all the alcohol gets into your blood (and therefore your brain) quickly, so the peak concentration in the brain is higher.
How quickly your stomach empties depends on several factors, most importantly the amount and type of food in your stomach. If there is little or no food in your stomach, it empties quickly. If there is a large volume of food, and especially if there is a lot of fat or protein, gastric emptying time is much slower. That's why you it's easier to get drunk on an empty stomach -- the alcohol gets into your brain faster.
So ... you will likely feel more effects of one 11% beer more than two 5.5% beers. Because: you are probably going to drink the one beer faster than the two beers. And the two beers will create 24 oz of volume in your stomach, and therefor slower gastric emptying time, compared to 12 oz of volume from one beer.