Problem 40 - Chemistry The Molecular Science

Question

Determine the chemical formulas for barium sulfate, magnesium nitrate, and sodium acetate. Each compound contains a monoatomic cation and a polyatomic anion. What are the names and electrical charges of these ions?

Step-by-Step Solution

Answer

Barium sulfate: \(\text{BaSO}_4\), Magnesium nitrate: \(\text{Mg}(\text{NO}_3)_2\), Sodium acetate: \(\text{NaC}_2\text{H}_3\text{O}_2\).

Step 1: Barium Sulfate Ion Identification

Barium sulfate is composed of barium ions \((\text{Ba}^{2+})\) and sulfate ions \((\text{SO}_4^{2-})\). The barium ion is a monoatomic cation with a charge of \(+2\), and the sulfate ion is a polyatomic anion with a charge of \(-2\).

Step 2: Formulate Barium Sulfate

To create a neutral compound, the charges of barium \((\text{Ba}^{2+})\) and sulfate \((\text{SO}_4^{2-})\) must balance. The formula is \(\text{BaSO}_4\).

Step 3: Magnesium Nitrate Ion Identification

Magnesium nitrate is made of magnesium ions \((\text{Mg}^{2+})\) and nitrate ions \((\text{NO}_3^{-})\). The magnesium ion is a monoatomic cation with a charge of \(+2\), and the nitrate ion is a polyatomic anion with a charge of \(-1\).

Step 4: Formulate Magnesium Nitrate

The magnesium ion \((\text{Mg}^{2+})\) will need two nitrate ions \((\text{NO}_3^{-})\) to balance the charges. The formula is \(\text{Mg}(\text{NO}_3)_2\).

Step 5: Sodium Acetate Ion Identification

Sodium acetate comprises sodium ions \((\text{Na}^+)\) and acetate ions \((\text{C}_2\text{H}_3\text{O}_2^-)\). The sodium ion is a monoatomic cation with a charge of \(+1\), and the acetate ion is a polyatomic anion with a charge of \(-1\).

Step 6: Formulate Sodium Acetate

The sodium ion \((\text{Na}^+)\) and acetate ion \((\text{C}_2\text{H}_3\text{O}_2^-)\) each carry charges of \(+1\) and \(-1\) respectively, balancing each other out. The formula is \(\text{NaC}_2\text{H}_3\text{O}_2\).

Key Concepts

Barium Sulfate

Barium sulfate is an inorganic compound with the chemical formula \( \text{BaSO}_4 \). It consists of barium ions \( (\text{Ba}^{2+}) \), which are positively charged cations, and sulfate ions \( (\text{SO}_4^{2-}) \), which are negatively charged anions. Both the barium and sulfate ions have a charge magnitude of 2, although their charges are opposite. This allows them to combine in a 1:1 ratio to form a neutral compound.

Here's how the charges balance:

• The barium ion has a charge of \(+2\).
• The sulfate ion has a charge of \(-2\).

So, when one barium ion pairs with one sulfate ion, the positive and negative charges cancel each other out, resulting in an electrically neutral compound.

Barium sulfate is widely used in the medical field as a radiocontrast agent due to its ability to absorb X-rays, making it ideal for imaging purposes.

Magnesium Nitrate

Magnesium nitrate, with the chemical formula \( \text{Mg}(\text{NO}_3)_2 \), is composed of magnesium ions \( (\text{Mg}^{2+}) \) and nitrate ions \( (\text{NO}_3^{-}) \). The magnesium ion is a monoatomic cation with a \(+2\) charge, whereas the nitrate ion is a polyatomic anion with a \(-1\) charge.

In order to form a neutral compound, you need two nitrate ions to balance the charge of one magnesium ion. The reasoning is as follows:

• One magnesium ion \( (\text{Mg}^{2+}) \) carries a \(+2\) charge.
• Each nitrate ion \( (\text{NO}_3^{-}) \) carries a \(-1\) charge.
• To balance the charges, it takes two nitrate ions to offset the \(+2\) charge of one magnesium ion.

Thus, the formula \( \text{Mg}(\text{NO}_3)_2 \) shows that two nitrate ions are combined with one magnesium ion, resulting in a stable, electrically neutral compound.

Magnesium nitrate is often used in fertilizers, providing essential nitrogen to plants.

Sodium Acetate

Sodium acetate, which has the formula \( \text{NaC}_2\text{H}_3\text{O}_2 \), consists of sodium ions \( (\text{Na}^+) \) and acetate ions \( (\text{C}_2\text{H}_3\text{O}_2^-) \). Both ions have charges of 1, but with opposite signs, allowing them to combine in a one-to-one ratio.

The charge considerations are straightforward:

• The sodium ion carries a \(+1\) charge.
• The acetate ion carries a \(-1\) charge.

Due to this exact matching in charges, the ions combine to form sodium acetate as an electrically neutral compound.

Sodium acetate has a variety of uses, including as a food preservative and in the creation of hot ice packs, where it crystallizes to release heat.