15 Aug, 2024
· Chemistry

What is the formula of chromium(III) carbonate

  • Cr₂(CO₃)₃
  • Cr(CO₃)₃
  • Cr₃CO₃
  • Cr₃(CO₃)₂
Short Answer
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Long Explanation

Explanation

Formula of Chromium(III) Carbonate

Chromium(III) carbonate consists of chromium ions with a +3 oxidation state and carbonate ions, which have a -2 charge. To determine the correct formula, we need to balance the charges of the ions.

For chromium ion:

Cr3+\text{Cr}^{3+}

For carbonate ion:

CO32−\text{CO}_3^{2-}

In order to balance the overall charge, we need a combination where the total positive charge from chromium equals the total negative charge from carbonate. The formula Cr2(CO3)3\text{Cr}_2(\text{CO}_3)_3 achieves this balance.

Detailed Charge Balance

The detailed formula can be represented as:

Cr2(CO3)3\text{Cr}_2(\text{CO}_3)_3

Where:

2×Cr3+=2×(+3)=+62 \times \text{Cr}^{3+} = 2 \times (+3) = +6 3×CO32−=3×(−2)=−63 \times \text{CO}_3^{2-} = 3 \times (-2) = -6

Conclusion

The formula ensuring charge neutrality is Cr2(CO3)3\text{Cr}_2(\text{CO}_3)_3.

Verified By
JC
Johnathan Clark

Chemistry Content Writer at Math AI

Johnathan Clark, with a Master's in Chemistry from the University of São Paulo, is a young high school chemistry teacher and part-time contract writer. His engaging classroom experiments translate into compelling written content that makes chemistry exciting and practical.

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Concept

Criss-Cross Method For Determining Ionic Formulas

Explanation of the Criss-cross Method for Determining Ionic Formulas

The criss-cross method is a straightforward technique used in chemistry to determine the formula of an ionic compound. This method relies on the charges of the ions involved and helps ensure the total charge of the compound is neutral.

Step-by-Step Process

  1. Identify the Ions:

    • Determine the cation (positively charged ion) and its charge.
    • Determine the anion (negatively charged ion) and its charge.

  2. Write the Symbols and Charges:

    • Represent the cation and anion with their chemical symbols and respective charges.

      For example, consider magnesium and chlorine:

      Mg2+,  Cl−\text{Mg}^{2+}, \ \ \text{Cl}^{-}

  3. Criss-Cross the Charges:

    • Use the absolute value of the charge on each ion as the subscript for the other ion.

    • Disregard the signs (+ or -).

      In our example: The charge on magnesium (Mg2+\text{Mg}^{2+}) is 2. This will become the subscript for chlorine. The charge on chlorine (Cl−\text{Cl}^{-}) is 1. This will become the subscript for magnesium.

      MgCl2\text{MgCl}_2

  4. Simplify the Formula If Necessary:

    • If the subscripts are common multiples, divide by the greatest common factor to simplify.

      If the result was something like Al2O6\text{Al}_2\text{O}_6, you would simplify to AlO3\text{AlO}_3.

Example

Let's determine the formula for aluminum sulfate using the criss-cross method:

Step 1: Identify the charges.

Aluminum ion:

Al3+\text{Al}^{3+}

Sulfate ion:

SO42−\text{SO}_4^{2-}

Step 2: Criss-cross the charges.

The charge of aluminum (Al3+)(\text{Al}^{3+}) becomes the subscript for sulfate (SO4)(\text{SO}_4).
The charge of sulfate (SO42−)(\text{SO}_4^{2-}) becomes the subscript for aluminum (Al)(\text{Al}).

Al2(SO4)3\text{Al}_2(\text{SO}_4)_3

Step 3: Simplify if needed.

In this example, no further simplification is required.

Hence, the formula for aluminum sulfate is:

Al2(SO4)3\text{Al}_2(\text{SO}_4)_3

Important Points

  • Always ensure the final formula is electrically neutral.
  • Double-check the subscripts to confirm they are the smallest whole numbers providing neutrality.

By following these steps, the criss-cross method simplifies the process of arriving at the correct ionic formula for compounds.

Concept

Balancing Charges Between Ions

Explanation

Balancing charges between ions is a fundamental concept in chemistry, especially crucial when writing chemical formulas and reactions. When ions combine to form neutral compounds, their charges must balance out.

Why it Matters

Ions are atoms or molecules that have gained or lost electrons, resulting in a net positive or negative charge. Cations are positively charged ions, while anions are negatively charged ions. In order for compounds to form, these charges must neutralize each other.

Key Steps

  1. Identify the Charges: Determine the ionic charges for each participating ion.
  2. Determine the Ratio: Find the smallest whole-number ratio of ions needed to balance the total positive and negative charges.

Example

Let's consider the formation of sodium chloride (NaCl):

  1. Sodium ion (Na+\text{Na}^+) has a charge of +1.
  2. Chloride ion (Cl−\text{Cl}^-) has a charge of -1.

To balance the charges:

Na++Cl−→NaCl\text{Na}^+ + \text{Cl}^- \rightarrow \text{NaCl}

The positive and negative charges are equal, and thus, the compound is neutral.

More Complex Example

For calcium chloride (CaCl2):

  1. Calcium ion (Ca2+\text{Ca}^{2+}) has a charge of +2.
  2. Chloride ion (Cl−\text{Cl}^-) has a charge of -1.

To balance the charges:

Ca2++2Cl−→CaCl2\text{Ca}^{2+} + 2 \text{Cl}^- \rightarrow \text{CaCl}_2

Here, one calcium ion combines with two chloride ions to balance the overall charge of the compound:

Total Positive Charge=+2Total Negative Charge=2×(−1)=−2\text{Total Positive Charge} = +2\\ \text{Total Negative Charge} = 2 \times (-1) = -2

Thus, the charges balance out perfectly, forming a neutral compound.

Understanding this concept ensures that chemical equations are correctly written and balanced, reflecting the true nature of the chemical compounds.