Problem 122 - Chemistry Matter and Change

Question

In the formula for sodium phosphate \(\left(\mathrm{Na}_{3} \mathrm{PO}_{4}\right),\) how many moles of sodium are represented? How many moles of phosphorus? How many moles of oxygen?

Step-by-Step Solution

Answer

In the formula for sodium phosphate \(\mathrm{Na_{3}PO_{4}}\), there are 3 moles of sodium (Na), 1 mole of phosphorus (P), and 4 moles of oxygen (O).

Step 1: Identify the elements and their corresponding subscripts in the formula

In the formula \(\mathrm{Na_{3}PO_{4}}\), there are three elements represented: sodium (Na), phosphorus (P), and oxygen (O). The subscript for each element represents its mole ratio in the formula.

Step 2: Determine the number of moles of Sodium

In the formula \(\mathrm{Na_{3}PO_{4}}\), the subscript for sodium (Na) is 3. This means that there are 3 moles of sodium in the formula.

Step 3: Determine the number of moles of Phosphorus

In the formula \(\mathrm{Na_{3}PO_{4}}\), the subscript for phosphorus (P) is 1, as there is no subscript written, which implies it is 1. This means that there is 1 mole of phosphorus in the formula.

Step 4: Determine the number of moles of Oxygen

In the formula \(\mathrm{Na_{3}PO_{4}}\), the subscript for oxygen (O) is 4. This means that there are 4 moles of oxygen in the formula.

Step 5: Summarize the results

In the formula for sodium phosphate \(\mathrm{Na_{3}PO_{4}}\), there are 3 moles of sodium, 1 mole of phosphorus, and 4 moles of oxygen.

Key Concepts

Mole Concept

The mole is a fundamental concept in chemistry that represents a specific quantity of substance. It is analogous to other counting units like dozen, but instead of 12, a mole consists of Avogadro's number, approximately \(6.022 \times 10^{23}\), representative particles. These particles can be atoms, molecules, ions, or other chemical entities. Understanding the mole is crucial because it allows chemists to count and quantify atoms and molecules in a scale that is manageable.When deciphering chemical formulas, the mole concept helps interpret the amount of each element present. For instance, in sodium phosphate (\(\mathrm{Na}_{3} \mathrm{PO}_{4}\)), the subscripts indicate how many moles of each element are in a mole of compound. Thus, for every mole of sodium phosphate, there are 3 moles of sodium atoms, 1 mole of phosphorus atoms, and 4 moles of oxygen atoms.

• A mole relates quantity to the mass of substance.
• It connects microscopic atomic-scale quantities to macroscopic amounts.
• Essential for stoichiometric calculations in reactions.

Molecular Composition

Molecular composition refers to the types and numbers of atoms that make up a chemical compound. It provides a formula that shows which elements are present and in what proportions. By examining a chemical formula, you can decipher the compound's molecular make-up.Using sodium phosphate (\(\mathrm{Na}_{3} \mathrm{PO}_{4}\)) as an example, three sodium (Na) atoms, one phosphorus (P) atom, and four oxygen (O) atoms make up the compound. This numerical representation of atoms is critical because it relates directly to the compound's properties and interactions.

• Molecular composition can determine chemical reactivity.
• Determines physical properties like melting and boiling points.
• Essential for understanding and predicting chemical reactions.

To understand the molecular composition well, one needs to interpret chemical symbols and subscripts correctly. Subscripts indicate how many atoms of each element are present, forming the basis for correctly identifying and studying any chemical compound.

Subscripts in Chemistry

In chemistry, subscripts are numerical indicators written slightly below and after a chemical symbol in a formula. They show the number of atoms of that element in one molecule of the compound. In simple terms, subscripts inform us about the mole ratio of the atoms in a compound, which is crucial for understanding its chemical structure and composition.For example, in \(\mathrm{Na}_{3} \mathrm{PO}_{4}\):

• The subscript 3 next to sodium (Na) denotes three sodium atoms per unit of sodium phosphate.
• A lack of subscript after phosphorus (P) implies there is one phosphorus atom present. In chemistry, a subscript of 1 is usually omitted for simplicity.
• The subscript 4 following oxygen (O) means there are four oxygen atoms per formula unit.

Subscripts are indispensable in determining the stoichiometry of chemical reactions. They assist in predicting how substances react and combine. Without an understanding of subscripts, it would be challenging to balance chemical equations correctly or to understand fuel efficiency in terms of combustion reactions.