Baking soda is basic. It must be used when you have an acidic liquid batter to neutralize the acid. If the batter is not acidic all the baking soda will do is taste bitter, and the batter will not rise. If too little baking soda is used when needed, again the batter may not rise. It is used to leaven delicate batters that do not contain an acid.
Some recipes call for both baking soda and baking powder.
These batters usually contain enough acid to react with a small amount of baking soda but not enough to produce the desired rising effect. Lemon juice - in addition to being a good acid for a salad dressing and a good acid for a marinade, will stop cut fruits and vegetables such as apples, bananas, avocados and artichokes from browning.