How to Find Hydrogen Carbonate Formula with the Criss-Cross Method
The correct answer and explanation is:
To find the formula of hydrogen carbonate using the criss-cross method, follow these steps:
- Identify the ions: The first step is to recognize the two ions involved. Hydrogen carbonate is an anion with the formula HCO₃⁻. The hydrogen ion (H⁺) is typically the cation in this case.
- Write the ion charges: The charge on the hydrogen ion is +1 (H⁺), and the charge on the hydrogen carbonate ion is -1 (HCO₃⁻).
- Criss-cross the charges: In the criss-cross method, the magnitude of each ion’s charge becomes the subscript of the other ion. This means you take the charge on the hydrogen ion (+1) and place it as a subscript to the hydrogen carbonate ion (HCO₃), and the charge on the hydrogen carbonate ion (-1) as a subscript to the hydrogen ion (H⁺).
- Adjust the subscripts: Since both ions have charges of 1 (±1), the criss-cross method leads to the formula HCO₃.
- Final formula: There are no further adjustments needed, as the subscripts are already in their simplest form. Therefore, the formula of hydrogen carbonate is HCO₃.
This method works by ensuring that the total positive charge and total negative charge in the compound are equal, which leads to a neutral compound overall. The criss-cross technique is particularly useful for binary ionic compounds but can be extended to polyatomic ions like hydrogen carbonate.
This straightforward approach to writing chemical formulas helps prevent mistakes, especially when dealing with more complex ions that involve multiple atoms. The criss-cross method allows you to quickly determine the simplest empirical formula, ensuring that the compound is electrically neutral and balanced in terms of charges.