Question

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

Short answer

There are (a) 6 hydrogen atoms in \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\), (b) 10 hydrogen atoms in \(\mathrm{Ca}\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{COO}\right)_{2}\), and (c) 12 hydrogen atoms in \(\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4}\).

Step-by-step solution

Identify the hydrogen atoms

In this molecule, we have the \(\mathrm{H}_{5}\) and \(\mathrm{OH}\) parts containing hydrogen atoms.

Count the hydrogen atoms

We have 5 hydrogen atoms in \(\mathrm{H}_{5}\) and 1 hydrogen atom in \(\mathrm{OH}\). So, there are 5 + 1 = 6 hydrogen atoms in total. (b) \(\mathrm{Ca}\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{COO}\right)_{2}\)

Identify the hydrogen atoms

In this molecule, there is a \(\mathrm{C}_{2} \mathrm{H}_{5}\) group that contains hydrogen atoms. Note that there is a subscript "2" outside the bracket, which means that there are two \(\mathrm{C}_{2} \mathrm{H}_{5}\) groups in the molecule.

Count the hydrogen atoms

There are 5 hydrogen atoms in each of the \(\mathrm{C}_{2} \mathrm{H}_{5}\) groups, and since there are two such groups, we have 5 × 2 = 10 hydrogen atoms in total. (c) \(\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4}\)

Identify the hydrogen atoms

In this molecule, there is an \(\mathrm{NH}_{4}\) group that contains hydrogen atoms. Note that there is a subscript "3" outside the bracket, which means there are three \(\mathrm{NH}_{4}\) groups in the molecule.

Count the hydrogen atoms

There are 4 hydrogen atoms in each of the \(\mathrm{NH}_{4}\) groups, and since there are three such groups, we have 4 × 3 = 12 hydrogen atoms in total. So, there are (a) 6 hydrogen atoms in \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\), (b) 10 hydrogen atoms in \(\mathrm{Ca}\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{COO}\right)_{2}\), and (c) 12 hydrogen atoms in \(\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4}\).

Key concepts

Chemical Formulas

Chemical formulas are short and convenient ways to represent chemical substances using symbols that denote the elements present. Each element in the formula is represented by its chemical symbol, like C for carbon, H for hydrogen, O for oxygen, Ca for calcium, and N for nitrogen.
The subscript numbers found after the symbols indicate how many atoms of each element are present in one molecule of the compound. For example, in the formula \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\), the numbers 2 and 5 tell us there are 2 carbon and 5 hydrogen atoms, respectively.
Understanding these formulas is crucial for identifying the number of different atoms in a molecule and allows chemists and students to visualize compounds in a simplified form. It's a fundamental step in exploring various chemical reactions and properties of compounds.

• Understanding the Symbols: Each element is represented by a unique symbol.
• Subscripts Indicate Quantity: The numbers point out how many of each element are present.
• Overall Structure: Provides insight into the makeup of molecules.

Molecular Structure

The molecular structure pertains to the arrangement of atoms within a molecule. Knowing the molecular structure helps us visualize how atoms are connected and the geometry of the molecule, which impacts its physical and chemical properties.
In our examples:

• The molecular structure of \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\) includes an alcohol group (OH), which classifies it as an alcohol.
• In \(\mathrm{Ca}(\mathrm{C}_2\mathrm{H}_5\mathrm{COO})_2\), understanding the structure reveals it as a calcium acetate compound with ion-connected acetate groups.
• The structure of \((\mathrm{NH}_4)_3\mathrm{PO}_4\) is made up of ammonium (NH₄) and phosphate (PO₄) groups, making it an ammonium phosphate.

Visualizing molecular structures helps us predict how molecules will interact physically and chemically with others. This is fundamental for deducing the behavior of substances in chemical reactions.

Stoichiometry

Stoichiometry is a concept in chemistry that revolves around the calculation of reactants and products in chemical reactions. It is based on the conservation of mass and the understanding that matter cannot be created or destroyed.

• In the scope of chemical formulas, stoichiometry allows us to determine the amount of each element in a given compound.
• In our exercise, hydrogen atom counting exemplifies this by systematically calculating the hydrogen presence in each molecule.

When we say \(\mathrm{Ca}(\mathrm{C}_2\mathrm{H}_5\mathrm{COO})_2\) contains 10 hydrogen atoms, we are using stoichiometric principles to count the atoms correctly. This process involves recognizing molecular subunits and applying multiplication skillfully to brackets in the formula.
To succeed in stoichiometry, it is essential to comprehend these principles:

• Balanced Equations: We need balanced chemical equations for precise calculations.
• Molecular Mass: Calculating molecular mass helps in understanding quantities involved.
• Proportionate Relationships: Recognizing mol units and proportions ensures accurate reactions analysis.

Through stoichiometry, chemists can predict the outcome of experiments and make informed decisions in research and application environments.