True or false? The mass number of an atom equals the sum of the protons and
electrons.

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

Stage in which a typical star has completely stopped fusion

The activation energy for the reaction no2(g)+co2(g)⟶no(g)+co(g) is ea = 300 kj/mol and the change in enthalpy for the reaction is δh = -100 kj/mol . what is the activation energy for the reverse reaction?