Question

Determine what is wrong with the chemical formula and write the correct chemical formula for each of the following compounds: (a) \(\left(\mathrm{NH}_{3}\right)_{2} \mathrm{CO}_{3}\) (ammonium carbonate), (b) \(\mathrm{CaOH}_{2}\) (calcium hydroxide), (c) \(\mathrm{CdSO}_{3}\) (cadmium sulfide), (d) \(\mathrm{ZnCrO}_{4}\) (zinc dichromate).

Short answer

(a) (NH_4)_2CO_3, (b) Ca(OH)_2, (c) CdS, (d) ZnCrO_4.

Step-by-step solution

Analyze Ammonium Carbonate

The given formula is \((\mathrm{NH}_3)_2 \mathrm{CO}_3\). Ammonium is \(\mathrm{NH}_4^+\), not \(\mathrm{NH}_3\), so the correct formula should use \(\mathrm{NH}_4^+\). Carbonate is \(\mathrm{CO}_3^{2-}\), requiring two ammonium ions to balance the charge. The correct formula is \((\mathrm{NH}_4)_2\mathrm{CO}_3\).

Analyze Calcium Hydroxide

The given formula is \(\mathrm{CaOH}_2\). Calcium is \(\mathrm{Ca}^{2+}\) and hydroxide is \(\mathrm{OH}^-\). Two hydroxide ions are needed to balance the charge of one calcium ion. The correct formula is \(\mathrm{Ca(OH)}_2\).

Analyze Cadmium Sulfide

The given formula is \(\mathrm{CdSO}_3\). Cadmium sulfide consists of cadmium \(\mathrm{Cd}^{2+}\) and sulfide \(\mathrm{S}^{2-}\), not \(\mathrm{SO}_3\), which is sulfite. The correct cadmium sulfide formula is \(\mathrm{CdS}\).

Analyze Zinc Dichromate

The given formula is \(\mathrm{ZnCrO}_4\). This incorrectly names chromate as dichromate. The correct name based on the given formula is zinc chromate, not zinc dichromate, which would be paired with \(\mathrm{Cr}_2\mathrm{O}_7^{2-}\). Therefore, if zinc chromate is intended, the formula is correct as it is \(\mathrm{ZnCrO}_4\).

Key concepts

Ammonium Carbonate

Ammonium carbonate is an interesting compound made up of ammonium and carbonate ions. Ammonium is commonly represented as \( \text{NH}_4^+ \), not \( \text{NH}_3 \), which is ammonia. This is an important distinction because ammonium carries a positive charge. On the other hand, the carbonate ion is represented as \( \text{CO}_3^{2-} \).

To form ammonium carbonate, the chemical formula must reflect the balance of these ions' charges. Since the carbonate ion has a \( 2- \) charge, you need two ammonium ions, each with a \( 1+ \) charge to balance it out. Hence, the correct formula is \((\text{NH}_4)_2\text{CO}_3\).

Here's a quick reason why accurately identifying ions is crucial:

• Ensures the chemical reaction qualitatively behaves as expected.
• Prevents the mistake of confusing similar but fundamentally different compounds.
• Guarantees charge neutrality in the compound's formation.

Without this precision, experiments and subsequent applications can go awry.

Calcium Hydroxide

Calcium hydroxide is an essential chemical compound with many practical applications. The formula might seem straightforward, but it's important to ensure every ion is correctly represented to reflect their charges.

The given formula was \( \text{CaOH}_2 \), which does not accurately reflect the charges involved. Calcium ions are \( \text{Ca}^{2+} \), while hydroxide ions are \( \text{OH}^- \). Since one calcium ion requires two hydroxide ions to balance its charge, the correct formulation should be \( \text{Ca(OH)}_2 \).

This improved understanding of the chemical formula has several benefits:

• Accurately depicts the ionic makeup of calcium hydroxide.
• Avoids potential errors in calculations or chemical equations.
• Recognizes the preservation of charge balance within the compound.

This compound is used in various applications, such as water treatment and construction, so it is essential to use the correct chemical formula.

Cadmium Sulfide

Cadmium sulfide is a fascinating compound due to its photoconductivity properties. However, it's easy to confuse the involved ions, as seen with the initial misidentification in its formula \( \text{CdSO}_3 \).

The correct formula for cadmium sulfide must include the cadmium ion \( \text{Cd}^{2+} \) and the sulfide ion \( \text{S}^{2-} \), not the sulfite ion \( \text{SO}_3^{2-} \). The equation simplifies to \( \text{CdS} \), ensuring both ions' charges are accurately canceled out.

Understanding the distinction between sulfide and other similar-sounding terms is critical:

• Maximizes accuracy in chemical characterization.
• Prevents confusion between distinct substances with different properties.
• Ensures correct documentation and interpretation within scientific research.

Cadmium sulfide's unique properties make it valuable in areas like electronics and nanotechnology.

Zinc Chromate

Zinc chromate's formula \( \text{ZnCrO}_4 \) correctly reflects its chromate constituent, but confusion arises when it's mistakenly called zinc dichromate. The distinction between chromate and dichromate is significant, as dichromate involves a different structural formula \( \text{Cr}_2\text{O}_7^{2-} \).

Zinc chromate consists of the zinc ion \( \text{Zn}^{2+} \) and chromate ion \( \text{CrO}_4^{2-} \). The balance in charges is straightforward in this instance, maintaining equilibrium in the compound.

Understanding these distinctions is vital:

• Ensures preciseness in chemical labeling and synthesis.
• Prevents mix-ups in safety protocols due to different chemical behaviors and hazards.
• Supports more informed usage in applications such as corrosion resistance coatings.

Zinc chromate is often employed in anti-corrosion paints, making its accurate identification critical.