Answer:
See Explanation
Step-by-step explanation:
The equation of the reaction is;
ZnO(s) + 2HNO3(aq) --------> Zn(NO3)2(aq) + H2O(l)
a) When you first add ZnO to aqueous HNO3, the powder dissolves as it mixes with the acid.
b) If the student keeps on adding more ZnO powder to the HNO3 after the reaction between the acid and metal oxide was complete, the powder will no longer dissolve in the acid. At this point, the reaction has attained equilibrium.