Problem 51 - Chemistry The Central Science

Question

How many hydrogen atoms are in each of the following: (a) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH},(\mathbf{b}) \mathrm{Ca}\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{COO}\right)_{2},(\mathbf{c})\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4} ?\)

Step-by-Step Solution

Answer

In conclusion, the number of hydrogen atoms in the given compounds are (a) 6 in \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\), (b) 12 in \(\mathrm{Ca}\left(\mathrm{C}_2\mathrm{H}_5\mathrm{COO}\right)_2\), and (c) 12 in \(\left(\mathrm{NH}_4\right)_3\mathrm{PO}_4\).

Step 1: Identify the subscript for hydrogen atoms in each compound

For each compound, we need to find the subscript that indicates the number of hydrogen atoms: (a) \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\): We have two parts with hydrogen atoms: \(\mathrm{H}_5\) and \(\mathrm{OH}\). (b) \(\mathrm{Ca}\left(\mathrm{C}_2\mathrm{H}_5\mathrm{COO}\right)_2\): We have hydrogen atoms in \(\mathrm{C}_2\mathrm{H}_5\) and \(\mathrm{COO}\). (c) \(\left(\mathrm{NH}_4\right)_3\mathrm{PO}_4\): We have hydrogen atoms in \(\mathrm{NH}_4\).

Step 2: Calculate the number of hydrogen atoms in each compound

Now, we will find the number of hydrogen atoms in each compound by multiplying the subscripts by any coefficients within the compound: (a) \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\): Using both parts with hydrogen atoms, we have \(5 + 1\) hydrogen atoms. Therefore, there are 6 hydrogen atoms in this compound. (b) \(\mathrm{Ca}\left(\mathrm{C}_2\mathrm{H}_5\mathrm{COO}\right)_2\): Here, we need to consider the coefficients: For \(\mathrm{C}_2\mathrm{H}_5\), we have \(5\) hydrogen atoms, and for \(\mathrm{COO}\), we have \(1\) hydrogen atom (from the \(\mathrm{OH}\) part). Since there is a subscript \(2\) after the bracket, we will need to multiply the total number of hydrogen atoms by this coefficient: \((5 + 1) \cdot 2 = 12\). Therefore, there are 12 hydrogen atoms in this compound. (c) \(\left(\mathrm{NH}_4\right)_3\mathrm{PO}_4\): In this compound, we have \(4\) hydrogen atoms in \(\mathrm{NH}_4\). Since there is a subscript \(3\) after the bracket, we will need to multiply the total number of hydrogen atoms by this coefficient: \(4 \cdot 3 = 12\). Therefore, there are 12 hydrogen atoms in this compound. In conclusion, there are: (a) 6 hydrogen atoms in \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\) (b) 12 hydrogen atoms in \(\mathrm{Ca}\left(\mathrm{C}_2\mathrm{H}_5\mathrm{COO}\right)_2\) (c) 12 hydrogen atoms in \(\left(\mathrm{NH}_4\right)_3\mathrm{PO}_4\)

Key Concepts

Counting Atoms

Counting atoms in a chemical formula is a fundamental skill in chemistry. It involves looking at the formula and identifying all the atoms present, along with their quantities. These quantities are represented by numbers called subscripts. Understanding how to count atoms helps us gain insights into the chemical composition of substances. For example, knowing how many atoms of each type are in a compound allows for a better understanding of chemical reactions.
When counting atoms, begin by identifying the elements in the formula. Then, look for the subscript next to each element’s symbol, which tells you how many atoms of that element are present. If there is no subscript, it means there is only one atom of that element. Additionally, if elements are within parentheses and have a subscript outside, multiply the subscript by the number of atoms inside the parentheses. This applies to polyatomic ions or when chemical formulas involve multiple groups of atoms. Mastering this skill simplifies tasks like balancing equations and predicting reaction outcomes.

Subscripts in Chemistry

In chemical formulas, subscripts play a crucial role by indicating the number of atoms of an element present in a compound. They are written immediately after the element symbol they describe. For instance, in the formula of water, \\(\mathrm{H}_2\mathrm{O}\), the subscript '2' tells us that there are two hydrogen atoms for every oxygen atom.
Subscripts are essential for showing the composition of compounds accurately. Without these subscripts, we wouldn’t be able to distinguish between compounds that contain the same elements in different proportions. It’s also important to remember that subscripts apply only to the elements they immediately follow. When dealing with parentheses, like in \\((\mathrm{NH}_4)_3\mathrm{PO}_4\), the subscript outside the bracket applies to all atoms inside, meaning all those atoms need to be multiplied by the subscript to get the correct count of atoms.
This understanding aids significantly in learning chemistry, enabling students to decipher complex formulas and prepare for further studies in stoichiometry and chemical reaction equations.

Molecular Compounds

Molecular compounds are formed when two or more nonmetals bond together by sharing electrons, a process known as covalent bonding. These compounds are characterized by their distinct molecules, which are collections of atoms bonded together in definite proportions. Molecular compounds like carbon dioxide (\(\mathrm{CO}_2\)) differ from ionic compounds in that they do not form lattice structures but rather exist as individual molecules.
The formulas for molecular compounds provide essential information about the number and type of atoms within a molecule. For instance, the formula for glucose, \\(\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6\), indicates six carbon, twelve hydrogen, and six oxygen atoms per molecule. Knowing how to interpret these formulas helps in recognizing the compound's properties, function, and its potential reactions in chemical processes.
Understanding molecular compounds is fundamental in numerous fields, including biology, environmental science, and medicine, because these compounds make up most of the substances we encounter in daily life. Recognizing molecular structures and their properties is key in analyzing biological organisms and their biochemical reactions.