4
Numbers above zero are significant, as well as any zeros that appear in between two non-zero numbers.
Heterogeneous
The mixture has more than one phase of matter in it.
Explanation:
For all of the questions, do the following calculation

As an example, I'll do question 1

In neutralization process or titration process, we use the formula;
(M1V1)H3PO4 = M2V2(Ca(OH)2)
M1 = 0.600 m
V1 = 10.0ml
M2 = unknown
V2 = 12.5ml
M1V1 = M2V2
0.6*10 = 12.5*M2
M2 = (0.6*10)/12.5 = 0.48m
Therefore, the answer is 0.480m
Barium Cynanide is the compound