Problem 24 - Chemistry A Molecular Approach

Question

Determine the number of each type of atom in each formula. a. \(\mathrm{Ca}\left(\mathrm{NO}_{2}\right)_{2}\) b. \(\mathrm{CuSO}_{4}\) c. \(\mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}\) d. \(\mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2}\)

Step-by-Step Solution

Answer

a. Ca: 1, N: 2, O: 4; b. Cu: 1, S: 1, O: 4; c. Al: 1, N: 3, O: 9; d. Mg: 1, H: 2, C: 2, O: 6.

Step 1: Identify the Elements in Calcium Nitrite

In the chemical formula \(\mathrm{Ca}(\mathrm{NO}_{2})_{2}\), identify the elements present. The compound contains calcium (Ca), nitrogen (N), and oxygen (O).

Step 2: Counting Atoms in Calcium Nitrite

For the compound \(\mathrm{Ca}(\mathrm{NO}_{2})_{2}\), we have one calcium atom. The subscript outside the parenthesis indicates there are two \(\mathrm{NO}_{2}\) groups, so multiply the subscripts of nitrogen and oxygen within the \(\mathrm{NO}_{2}\) group by 2. This gives 2 nitrogen atoms and 2*2 oxygen atoms, which is 4 oxygen atoms.

Step 3: Identify the Elements in Copper(II) Sulfate

In the chemical formula \(\mathrm{CuSO}_{4}\), identify the elements present. The compound contains copper (Cu), sulfur (S), and oxygen (O).

Step 4: Counting Atoms in Copper(II) Sulfate

The compound \(\mathrm{CuSO}_{4}\) has one copper atom, one sulfur atom, and four oxygen atoms, as indicated by the subscript 4 next to the oxygen.

Step 5: Identify the Elements in Aluminum Nitrate

In the chemical formula \(\mathrm{Al}(\mathrm{NO}_{3})_{3}\), identify the elements present. The compound contains aluminum (Al), nitrogen (N), and oxygen (O).

Step 6: Counting Atoms in Aluminum Nitrate

For \(\mathrm{Al}(\mathrm{NO}_{3})_{3}\), there is one aluminum atom. Multiplying the subscripts of the elements in the \(\mathrm{NO}_{3}\) group by 3, we get 3 nitrogen atoms and 3*3 oxygen atoms, which equals 9 oxygen atoms.

Step 7: Identify the Elements in Magnesium Bicarbonate

In the chemical formula \(\mathrm{Mg}(\mathrm{HCO}_{3})_{2}\), identify the elements present. The compound contains magnesium (Mg), hydrogen (H), carbon (C), and oxygen (O).

Step 8: Counting Atoms in Magnesium Bicarbonate

For \(\mathrm{Mg}(\mathrm{HCO}_{3})_{2}\), there is one magnesium atom. Since there are two \(\mathrm{HCO}_{3}\) groups, multiply the subscripts of hydrogen, carbon, and oxygen within the \(\mathrm{HCO}_{3}\) group by 2. This yields 2 hydrogen atoms, 2 carbon atoms, and 2*3 oxygen atoms which equal 6 oxygen atoms.

Key Concepts

Stoichiometry

Stoichiometry is a foundational principle in chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It is based on the conservation of mass and the concept that elements are neither created nor destroyed in chemical reactions. This means that the number of atoms of each element present in the reactants must be equal to the number of atoms of those same elements in the products.

To understand stoichiometry, one must be familiar with a chemical formula, which tells us the types and numbers of atoms in a molecule. For instance, in the formula \(\mathrm{Ca}(\mathrm{NO}_{2})_{2}\), stoichiometry allows us to calculate that there is one calcium atom (Ca), two nitrogen atoms (N), and four oxygen atoms (O). Such calculations are crucial when determining how much of each reactant is needed to produce a desired amount of product. It's important to note that stoichiometry can also apply to ionic compounds where the formula represents the simplest ratio of ions in the compound.

The improvement advice for exercises involving stoichiometry is to ensure consistency in the method of counting atoms and to understand the significance of subscripts and parentheses in chemical formulas. For instance, subscripts outside parentheses should be multiplied with each element inside the parentheses to ascertain the atom count.

Chemical Nomenclature

Chemical nomenclature is the systemic way of naming chemicals to ensure that each has a unique and universally accepted name. This system helps scientists communicate without ambiguity. For compounds like \(\mathrm{CuSO}_{4}\), scientific nomenclature dictates that it is named copper(II) sulfate, which indicates that copper has a +2 oxidation state and is combined with sulfate, \(\mathrm{SO}_{4}^{2-}\).

Understanding naming conventions is key to mastering chemistry. It assists in identifying the composition of molecules and the kind of ions involved. Moreover, it gives insights into the potential properties and reactions of the substance. For example, the '(II)' in copper(II) sulfate tells you that copper has a valency of 2, which can impact how it interacts with other substances.

When improving your grasp of chemical nomenclature, focus on the rules for different types of compounds (ionic, molecular, acids, etc.) and the use of Roman numerals to denote transition metal cations' charges. Let's take \(\mathrm{Al}(\mathrm{NO}_{3})_{3}\) as another example; it is named aluminum nitrate, indicating that it contains aluminum ions and nitrate ions.

Molecular Composition

Molecular composition reveals the number and type of atoms that constitute a single molecule of a substance, which in turn, defines its chemical properties and behavior. It's determined by examining a compound's chemical formula. For instance, \(\mathrm{Mg}(\mathrm{HCO}_{3})_{2}\) shows that a molecule of magnesium bicarbonate contains one magnesium atom, two hydrogen atoms, two carbon atoms, and six oxygen atoms.

Molecular composition is essential for calculating molecular mass, understanding molecular geometry, and predicting the physical and chemical properties of the substance. Furthermore, it serves as the basis for chemical equations which depict the reactants and products in chemical reactions.

To improve understanding of molecular composition, focus on the conventions used in writing chemical formulas, such as the placement and significance of subscripts and coefficients. Practice interpreting formulas to determine the number of each type of atom present—it's often helpful to draw a visual representation of the molecule, showing all atoms and their respective bonds, to aid your understanding.