# What is the molecular formula of the nitrate of a metal Q that forms a carbonate of the form QCO3?

A metal $$\ce{Q}$$ forms a carbonate and a nitrate. The molecular formula of the carbonate of $$\ce{Q}$$ is $$\ce{QCO3}$$. What is the molecular formula of the nitrate of $$\ce{Q}$$?

The answer says it is $$\ce{Q(NO2)3}$$ which I think is incorrect; I think the answer should be $$\ce{Q(NO3)2}$$. Am I right?

• Yes, you were right. – Jason Patterson Oct 17 '14 at 13:46
• OK, this takes my back to my high school days when I have to deal with my chemistry/gym teacher, which I previously mentioned on this forum (surely to the disbelief of many), which may be a barometer on the quality of science education in some locales. The obvious correct answer is, as you have argued because you have some elemental foundation in chemistry. The question most likely suffers from a typo. Those unsure should not be your first source on chemistry. – AJKOER 3 mins ago – AJKOER Mar 4 at 13:09

The carbonate anion is $\ce{CO3^{2-}}$. This tells us that the metal cation is doubly positively charged: $$\ce{Q^{2+} + CO3^{2-} -> QCO3}$$
1. the nitrite anion $\ce{NO2^-}$
2. the nitrate anion $\ce{NO3^-}$
Since the question you're concerned with asks for the formula of the nitrate of $\ce{Q}$, the correct answer would be $\ce{Q(NO3)2}$.
However, the compound $\ce{Q(NO2)2}$ is, at least from a charge perspective, also correct. But that is the nitrite of $\ce{Q}$.