I guess you are asking what world should go at the beginning of the sentence. If I am right, it is energy.
if this is true or false its true hope i helped
Answer:
Law of Conservation of Energy
Explanation:
3Zn + 8HNO3 ---> 3Zn(NO3)2 + 4H2O + 2NO IF IT IS COLD AND DILUT NITRIC ACID .
IF IT IS HOT AND CONCENTRATED THEN:
Zn+ 4HNO3 ---> Zn(NO3)2 +2H2O +2NO2