Yes. The "average weight" for an 11 month-old baby is about 21 pounds. However, the important thing is how a baby has been growing and developing, as noted at each check-up and as shown on his growth charts. Most babies are either above or below "average weight" (much of it is genetic or familial), but when one averages out thousands of babies' weights, the answer is about 21 pounds at 11 months.
Doesn't matter. What does matter is how your child has been growing. At each visit with the pediatrician your child's weight and height will be plotted on their growth chart and over time you and the doctor can follow your child's growth. It is important to follow the trend over time. If your child is below or above average but has been growing well and following their growth percentile they are likely healthy.