This is an ionic compound because there is a metal (iron) bound to a nonmetal (the polyatomic ion nitrate). Iron, \(\displaystyle (Fe)\) is a transition metal, which means it can take on multiple different charges. To find the charge of iron in this compound we must not that the compound as a whole is neutral. Also we must know the charge on the nitrate ion, \(\displaystyle (NO_3^-)\), is negative one. To balance the two nitrate ions with one iron atom, the iron must carry a positive two charge. In naming ionic compounds with transition metals, we must use Roman numerals to indicate the charge on the metal. Thus the name of this compound is iron(II) nitrate.

\(\displaystyle PbCl_{2}\) is the correct answer because it takes two chloride ions to balance the positive two charge on the lead atom. lead (II) refers to the ion of lead with a \(\displaystyle +2\) charge instead of Lead (IV) which refers to the ion with a \(\displaystyle +4\) charge. Note that roman numerals are used with elements that can form more than one cation (generally transition metals).

For this question, you need to have the charges of polyatomic ions memorized. This will tell you that of the answer choices only the carbonate ion has a net charge of \(\displaystyle -2\).

Chlorate: \(\displaystyle ClO_{3}^-\)

Nitrite: \(\displaystyle NO_{2}^-\)

Phosphate: \(\displaystyle PO_{4}^{3-}\)

Carbonate: \(\displaystyle CO_{3}^{2-}\)

_{\(\displaystyle NH_4\)} and \(\displaystyle NO_3\) are known as polyatomic ions. When a compound made up of polyatomic ions ionizes in water, it separates into the original polyatomic ions, not the individual elements.

\(\displaystyle NH_4NO_3\rightarrow NH_4^++NO_3^-\)

Phosphoric acid combines a single phosphate ion with three hydrogen ions. The correct molecular formula is \(\displaystyle H_{3}PO_{4}\).

\(\displaystyle PO_{4}^{3-}+3H^{+}\rightarrow H_{3}PO_{4}\)

Sulfate is a polyatomic ion that is composed of one sulfur atom and four oxygen atoms. The ion has a net charge of \(\displaystyle \small -2\).

\(\displaystyle SO_4^{-2}\)

Since sodium ions have a charge of \(\displaystyle \small +1\), we must use two atoms of sodium in order to result in a neutrally charged compound.

\(\displaystyle 2Na^+\)

This makes the neutral chemical compound \(\displaystyle Na_{2}SO_{4}\).

Since we know the percentages by mass, we can convert them into grams by imagining a 100-gram sample of the mystery compound. At that point, we can determine how many moles are present for each element:

\(\displaystyle 40\%\ C=40g\ C*\frac{1mol\ C}{12g\ C}= 3.33 mol\ C\)

\(\displaystyle 6.7\%\ H=6.7g\ H*\frac{1mol\ H}{1g\ H}= 6.7 mol\ H\)

\(\displaystyle 53.3\%\ O=53.3g\ O*\frac{1mol\ O}{16g\ O}= 3.33 mol\ O\)

By dividing each molar amount by the smallest molar amount (in this case 3.33), we can find the elemental ratios.

\(\displaystyle C:H:O=\frac{3.33}{3.33}:\frac{6.7}{3.33}:\frac{3.33}{3.33}=1:2:1\)

This means that the empirical formula for this compound is \(\displaystyle CH_{2}O\).

Since we were told that the molecular formula is six times as heavy as the empirical formula, we need to multiply each elemental amount in the empirical formula by six. After doing this, we find that the molecular formula is \(\displaystyle C_{6}H_{12}O_{6}\).

Carboxylic acids are formed by a carbon atom with a double bond to an oxygen atom, as well as an -oh substituent. This leaves one remaining bond for the carbon atom, allowing it to bind to a larger molecular component. The name for a carboxylic acid bound to a larger molecule is a "carboxyl group."

Carbonyl groups are formed when a carbon atom forms a doubl bond with an oxygen atom and any two other substituents. Carboxylic acids, aldehydes, ketones, esters, and amides are all carbonyl functional groups.

An ester is formed when a carbon forms a double bond with an oxygen and a single bond with a second oxygen atom. The second oxygen is generally incorporated into the backbone structure of the molecule, rather than as a single substituent to the carbon.

An ether is formed by an oxygen atom bound to two other atoms (usually carbons).

Ionic bonds generally occur between metal and nonmetal ions, while covalent bonds usually occur between two nonmetal atoms. The compounds containing sodium, iron, silver, calcium, and rubidium will all contain ionic bonds involving these elements.

The answer \(\displaystyle F_2,\ H_2O,\ CO_2\) is the only answer without any metal atoms, indicating that the bonds in these molecules will be covalent.

Hydrogen bonds are present in molecules in which hydrogen atoms are bound to highly electronegative atoms, namely oxygen, fluorine, or nitrogen. These bonds are extremely polar, resulting in a partial positive charge on the hydrogen atoms and a partial negative charge on the more electronegative atom.

Of the given answer options, methane (\(\displaystyle CH_4\)), is the only one that does not involve a hydrogen atom bound to an oxygen, nitrogen, or fluorine. It cannot demonstrate hydrogen bonding.

Note that glucose (\(\displaystyle C_6H_{12}O_6\)), as well as most other sugars, contain aldehyde or hydroxyl groups. These consist of -OH bonds, which allow for hydrogen bonding.