Baking Soda is a leavening agent. It makes cake batter to rise.
Crispy is the result of temperature and method.
Most restaurants prepare chicken in a commerical Deep Fryer in which the chicken is submerged in and cooked for 20 minutes in several gallons of hot oil. The nearest a home cook can come to duplicating restaurant chicken is to fry chicken in 3" of HOT - not smoking - oil.
I do not normally use this restaurant recipe at home as my kitchen is very small. You'll need two shallow pans and a skillet.
Heat the oil in a large skillet. While it is heating prepare the chicien
Pan 1: Mix one egg with a quart of milk for egg wash. Mix well
pan 2: Mix flour with salt and a little pepper. I use about 1 1/2 tsp salt to each 2 cups of flour. Mix well.
Clean the chicken, rinse it well and pat dry. Prepare the legs and thighs first as they take longer to cook than breast and wings. Starting with the thighs dip each peice in the egg wash and flour and repeat one time. Do this to each piece of chicken. Drop each piece into the hot oil - leaving the wings to last. Cook it uncovered if you want crispy chicken. .
You will have 7-8 minutes after you put the last wing in the skiller to put the rest of your meal together and plate it before the chicken is ready to remove and drain on towels before you serve it.