Identify the ions present based on the observations from the chemical tests.

Here is the completed table:

a) i)

• Conclusion: $\boxed{\text{NH}_4^+ \text{ ions present}}$

a) ii)

• Conclusion: $\boxed{\text{NO}_3^- \text{ ions present}}$

b) i)

• Observation: $\boxed{\text{Dirty green precipitate formed}}$

b) ii)

• Observation: $\boxed{\text{White precipitate formed, insoluble in dilute HCl}}$

c) i)

• Conclusion: $\boxed{\text{Ca}^{2+} \text{ ions present}}$

c) ii)

• Conclusion: $\boxed{\text{CO}_3^{2-} \text{ ions present}}$