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Chapter 3: Problem 13

How many hydrogen atoms are represented in each formula? (a) \(\mathrm{Al}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{3}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\) (c) \(\mathrm{NH}_{4} \mathrm{OH}\) (d) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{CH}_{3}\)

Short Answer

Expert verified
(a) 9 H, (b) 8 H, (c) 5 H, (d) 10 H

Step by step solution

01

Identify hydrogen atoms in formula (a)

In the formula \(\text{Al}\big(\text{C}_2\text{H}_3\text{O}_2\big)_3\), notice that the acetate ion \( \text{C}_2\text{H}_3\text{O}_2 \) contains 3 hydrogen atoms. Since there are 3 acetate ions, multiply the number of hydrogen atoms by 3: \(3 \times 3 = 9.\)
02

Tally hydrogen atoms in formula (b)

In the molecule \( \text{CH}_3\text{CH}_2\text{CH}_2\text{OH} \), count the hydrogen atoms as follows: \( \text{CH}_3 = 3 \thinspace \text{H}, \text{CH}_2 = 2 \thinspace \text{H}, \text{CH}_2 = 2 \thinspace \text{H}, \text{OH} = 1 \thinspace \text{H}. \) Add them together: \( 3 + 2 + 2 + 1 = 8. \)
03

Count hydrogen atoms in formula (c)

For \( \text{NH}_4\text{OH} \), sum the hydrogen atoms: \( \text{NH}_4 \) has 4 hydrogen atoms and \(\text{OH}\) has 1 hydrogen atom. Therefore: \( 4 + 1 = 5. \)
04

Sum hydrogen atoms in formula (d)

In the molecule \( \text{C}_6\text{H}_5\text{CH}_2\text{CH}_3 \), determine the number of hydrogen atoms: \( \text{C}_6\text{H}_5 \) has 5 hydrogen atoms, \( \text{CH}_2 \) has 2, and \( \text{CH}_3 \) has 3. Therefore: \( 5 + 2 + 3 = 10. \)

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

chemical formula analysis
Understanding chemical formulas is crucial in chemistry. A chemical formula represents the composition of a molecule using chemical symbols and numbers. Each symbol stands for an element, and the subscript numbers denote how many atoms of each element are present.
  • The subscript directly after a symbol means the number of that atom in the molecule.
  • If a formula is within parentheses and has a subscript outside, multiply all atoms inside the parentheses by that subscript.
For example, in the formula \(\text{Al}\big(\text{C}_2\text{H}_3\text{O}_2\big)_3\), acetate ions \(\text{C}_2\text{H}_3\text{O}_2\) contain 3 hydrogen atoms each, and they are multiplied by 3. Hence, \ 3 * 3 = 9 \ hydrogen atoms. Knowing these rules simplifies analyzing and counting atoms in any chemical formula.
stoichiometry
Stoichiometry involves the study of the quantities of reactants and products in chemical reactions. It is essential for solving problems related to chemical formula analysis.
To count atoms in different formulas, follow the rules of stoichiometry:
  • Identify the quantity of each type of atom.
  • Multiply the number of atoms by coefficients and subscripts accordingly.
For example, in \(\text{NH}_4\text{OH}\), you count the hydrogen atoms as follows: 4 hydrogen atoms from \ \text{NH}_4 \ and 1 hydrogen atom from \ \text{OH} \, summing up to \ 4 + 1 = 5 \ hydrogen atoms. Stoichiometry ensures accurate quantification in formulatic calculations.
molecular hydrogen count
Counting the number of hydrogen atoms in a molecule is a straightforward but essential task in chemistry. Hydrogen atoms are often present in significant quantities in organic molecules.
Take the example of \(\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}\). The molecule includes 3, 2, 2, and 1 hydrogen atoms from different groups respectively. Summing them up, \ 3 + 2 + 2 + 1 = 8 \ hydrogen atoms are present in the whole molecule.
  • CH3 contributes 3.
  • CH2 groups add 2 each.
  • OH also adds 1 hydrogen atom.
Such calculations are critical for understanding the complete structure and properties of molecules.
organic chemistry
Organic chemistry studies the structure, properties, and reactions of organic compounds, primarily made of carbon and hydrogen. Understanding the molecular composition, including counting hydrogen atoms, is key in this field.
For instance, the molecule \(\text{C}_6\text{H}_5\text{CH}_2\text{CH}_3\) contains:
  • 5 hydrogen atoms in the \ \text{C}_6\text{H}_5 \ part.
  • 2 from \ \text{CH}_2 \ and
  • 3 from \ \text{CH}_3 \.
Adding these quantities, a total of 10 hydrogen atoms are found. A deep understanding of organic chemical formulas helps predict reactivities and behaviors of compounds. This knowledge is fundamental in fields like biochemistry, pharmacology, and materials science.

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Most popular questions from this chapter

Write the name and number of atoms of each element in each of the following compounds: (a) \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) (b) \(\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}\) (c) \(\mathrm{Co}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{2}\) (d) \(\mathrm{CH}_{3} \mathrm{COCH}_{3}\) (e) \(\mathrm{K}_{2} \mathrm{CO}_{3}\) (f) \(\mathrm{Cu}_{3}\left(\mathrm{PO}_{4}\right)_{2}\) (g) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\) (h) \(\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\)

How many total atoms are represented in each formula? (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\) (b) \(\mathrm{KAl}\left(\mathrm{SO}_{4}\right)_{2}\) (c) \(\mathrm{NH}_{4} \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\) (d) \(\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{Cl}_{2}\)

How many oxygen atoms are represented in each formula? (a) \(\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{3}\) (b) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) (c) \(\mathrm{Ba}\left(\mathrm{ClO}_{3}\right)_{2}\) (d) \(\mathrm{Fe}_{2}\left(\mathrm{Cr}_{2} \mathrm{O}_{7}\right)_{3}\)

One cup of Raisin Bran provides \(60 . \%\) of the U.S. recommended daily allowance (RDA) of iron. (a) If the cereal provides \(11 \mathrm{mg}\) of iron, what is the U.S. RDA for \(\mathrm{Fe}\) ? (b) When the iron in the cereal is extracted, it is found to be the pure element. What is the volume of iron in a cup of the cereal?

Many foods contain interesting compounds that give them their flavors and smells. Some of these compounds are listed below with the chemical composition given after each name. Write the formulas for these compounds. (a) Allicin gives garlic its flavor (6 carbons, 10 hydrogens, 1 oxygen, and 2 sulfurs). (b) Capsaicin gives peppers their heat (18 carbons, 27 hydrogens, 1 nitrogen, and 3 oxygens). (c) Limonene gives oranges their fragrance (10 carbons and 16 hydrogens).
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