# Question #bf7ca

Jun 6, 2017

$\text{Zn"(s) + 2"AgNO"_3 (aq) rarr "Zn(NO"_3")"_2 (aq) + 2"Ag} \left(s\right)$

#### Explanation:

Let's look at our reactants and products,

Reactants

• zinc metal. We write this in the chemical equation as the chemical symbol for zinc, $\text{Zn}$. Often times a species in a chemical equation is followed by its physical state in parentheses:

$\left(s\right)$ for a solid substance

$\left(l\right)$ for a liquid substance

$\left(g\right)$ for a gaseous substance

$\left(a q\right)$ for a substance dissolved in aqueous solution

Most periodic tables will indicate the state of matter for each element, usually via a color code. Zinc is a solid metal, so we can follow it with the symbol $\left(s\right)$ in the reaction

• silver nitrate. This is a compound formed from the electrostatic attraction between a cationic silver atom, ${\text{Ag}}^{+}$, and the anionic nitrate species, ${\text{NO}}_{3}^{-}$, so its formula is ${\text{AgNO}}_{3}$.

As for the state of matter, we must realize something about this reaction. Most all ionic substances are solid at room temperature, but for this reaction we won't write $\left(s\right)$ next to it, and here's the simple reason why. When two pure solids are interacting, nothing chemically is really happening; you can squeeze the two substances together, but no new substances will form. Therefore, it is implied that the ${\text{AgNO}}_{3}$ species is dissolved in aqueous solution, so we follow it with $\left(a q\right)$.

Products

• zinc nitrate. This compound is formed from the attraction between the zinc ion ${\text{Zn}}^{2 +}$ and the nitrate ion, so its formula is ${\text{Zn(NO"_3")}}_{2}$.

Its state of matter is the same situation as the silver nitrate, and is dissolved in solution, so it's followed by $\left(a q\right)$.

• silver metal. Likewise for zinc metal, this is simply the chemical symbol of silver, $\text{Ag}$ followed by its state of matter, solid, so it is $\text{Ag} \left(s\right)$

We can now form an unbalanced (no coefficients) chemical equation from this:

$\text{Zn"(s) + "AgNO"_3 (aq) rarr "Zn(NO"_3")"_2 (aq) + "Ag} \left(s\right)$

If you'll notice, there are two nitrate ions on the right side, and one on the left. To balance the nitrate species, we can place a $2$ before the silver nitrate on the left side:

$\text{Zn"(s) + color(blue)(2)"AgNO"_3 (aq) rarr "Zn(NO"_3")"_2 (aq) + "Ag} \left(s\right)$

What you may notice now is that now the silvers are unbalanced; there are two on the left and one on the right. We can fix this by placing a $2$ in front of the silver on the right side:

$\text{Zn"(s) + color(blue)(2)"AgNO"_3 (aq) rarr "Zn(NO"_3")"_2 (aq) + color(red)(2)"Ag} \left(s\right)$

Now, all the species are present equally on both sides of the reaction arrow, so this equation is balanced.