Answer:
The substance is a mixture because it left a white powder in the beaker when boiled.
Explanation:
Answer:
2. Co(NO3)2 + H2
Explanation:
Hello,
In this case, we are evidencing a simple displacement reaction wherein the cobalt is able displace the hydrogen to produce cobalt (II) nitrate and gaseous hydrogen as a result of cobalt's higher activity:

Therefore, answer is 2. Co(NO3)2 + H2.
Best regards.