yes some chemical reactions are harmful to us. as digestion of food, photosynthesis, decomposition of organic waste are some examples of the useful chemical reactions.
Anabolic reactions form organs and tissues of the body.
Two types of displacement reactions are known:- single displacement- double displacement
burning fuel reactions are useful because when energy is released and be converted into different forms they do useful work.. sorry find out your self about what useful works ......
Because they let us get around a lot eg like in our cars.But some reactions cause a lot of pollution so you cant use them to often. but other reactions are good!
make it useful for testing for signs of carbonation reactions in concrete
For example the reaction with water.
Your question does not contain enough information to be answered. What reactions? In what? To what?
Catabolism is breaking molecules down into smaller molecules (to get energy). You can remember this if you've ever had a cat -- they break things. Anabolism is the opposite: building things up (to make useful stuff). Now look up the definition of synthesis.
Combustion reactions are useful to humans because they provide heat energy for cooking, heating, and generating electricity. They also power vehicles and machinery by converting chemical energy into kinetic energy.
Activity series are useful for single displacement reactions.
I don't know look it your self