Question

How many of the indicated atoms are represented by each chemical formula: (a) carbon atoms in \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{COOCH}_{3}\), (b) oxygen atoms in \(\mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2}\), (c) hydrogen atoms in \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}\) ?

Short answer

(a) There are 6 carbon atoms in \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{COOCH}_{3}\). (b) There are 6 oxygen atoms in \(\mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2}\). (c) There are 9 hydrogen atoms in \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}\).

Step-by-step solution

Count the carbon atoms in \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{COOCH}_{3}\)

In the given formula, \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{COOCH}_{3}\), there are the following carbon atoms: - 4 from \(\mathrm{C}_{4}\) - 1 from \(\mathrm{COOCH}_{3}\), which is the carbon in the middle of the group - 1 from \(\mathrm{COOCH}_{3}\), which is the carbon in the \(\mathrm{CH}_{3}\) part of the group In total, there are 4 + 1 + 1 = 6 carbon atoms represented in the formula.

Count the oxygen atoms in \(\mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2}\)

In the given formula, \(\mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2}\), there are the following oxygen atoms: - 3 from each \(\mathrm{ClO}_{3}\) group - Since there are 2 \(\mathrm{ClO}_{3}\) groups (due to the subscript 2 in the formula), we have 2 × 3 = 6 oxygen atoms in total.

Count the hydrogen atoms in \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}\)

In the given formula, \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}\), there are the following hydrogen atoms: - 4 from each \(\mathrm{NH}_{4}\) group - Since there are 2 \(\mathrm{NH}_{4}\) groups (due to the subscript 2 in the formula), we have 2 × 4 = 8 hydrogen atoms from the \(\mathrm{NH}_{4}\) groups - 1 more hydrogen atom from the \(\mathrm{HPO}_{4}\) group In total, there are 8 + 1 = 9 hydrogen atoms represented in the formula.

Key concepts

Counting Atoms in Chemical Compounds

Understanding the number of atoms in a chemical formula is fundamental when studying chemistry. It's like reading a recipe; knowing the ingredients and their amounts are essential to the outcome. Consider the chemical formula C₄H₈COOCH₃. What looks like a jumble of letters and numbers to the untrained eye actually reveals the precise amount and types of atoms involved.

In this compound, the subscript numbers indicate how many atoms of the preceding element we have. For carbon (C), there is a subscript 4, identifying four carbon atoms. The group COOCH₃ also includes carbon atoms, one within the COO and another within the CH₃. Therefore, adding them up (4 from C₄, 1 from COO, and 1 from CH₃) gives us a total of 6 carbon atoms.

Counting atoms correctly is more than just arithmetic; it's about understanding the molecular structure. When you see the chemical formula for a compound, you are looking at the blueprint of that compound's molecular architecture.

Interpreting Chemical Formulas

Chemical formulas aren't there just to intimidate you; they are the language of chemistry. Learning to interpret them is like learning to read a new alphabet in chemistry. Take the formula Ca(ClO₃)₂ as an example. This tells us we have a calcium atom (Ca) associated with two groups of ClO₃. Each ClO₃ group contains three oxygen atoms, as indicated by the subscript. Since there are two of these groups, we do the quick math: 2 groups times 3 oxygen atoms equals 6 oxygen atoms in total.

Grouping and Multiplication in Chemical Formulas

It's important to note how parentheses play a role. They group certain atoms together, much like using brackets in math. When these atomic groups have a subscript outside the parentheses, it means we multiply the number of each atom inside by that subscript. If you can understand the language of chemical formulas, it unlocks the ability to comprehend the composition and properties of chemical substances.

Molecular Composition

Let's delve deeper into the molecular composition, exemplified by the formula (NH₄)₂HPO₄. The molecule's composition is a portrait of the compound, depicting how different atom types come together to form the whole. In this particular formula, we can infer that two ammonium groups (NH₄) are present due to the subscript 2. Each ammonium group has 4 hydrogen atoms, which add up to 8 when considering both groups.

Additionally, the molecular structure includes a hydrogen phosphate group HPO₄, contributing one more hydrogen to the total count. Sometimes, atoms are not equally distributed throughout the molecule. This uneven distribution often influences the molecule's shape and reactivity. With 9 hydrogen atoms, we get a clearer vision of this compound's molecular landscape. Knowing the molecular composition aids in visualizing the molecule's geometrical structure, which is pivotal for anticipating its chemical behavior and interactions.