Find the formula for lithium chromate. Please show a method on how to solve this and how to approach other problems of this type.
The Correct Answer and Explanation is:
To find the formula for lithium chromate, you need to understand how to balance the charges of the ions involved. Here’s a step-by-step approach to solving this type of problem.
Step 1: Identify the ions involved
- Lithium (Li): Lithium is a Group 1 metal and forms a Li⁺ ion.
- Chromate (CrO₄²⁻): Chromate is a polyatomic ion with a charge of 2-.
Step 2: Balance the charges
The goal is to combine the ions in such a way that the total charge of the compound is zero. The charges on lithium and chromate need to balance out.
- Each lithium ion (Li⁺) has a charge of +1.
- The chromate ion (CrO₄²⁻) has a charge of -2.
To balance the charges, you need two lithium ions to neutralize the charge of one chromate ion, because:
- 2 Li⁺ ions × (+1 charge) = +2
- 1 CrO₄²⁻ ion × (-2 charge) = -2
Step 3: Write the formula
Since you need two lithium ions to balance the charge of one chromate ion, the formula for lithium chromate is:
- Li₂CrO₄
Step 4: Apply this method to other compounds
This method can be applied to many ionic compounds:
- Identify the ions and their charges.
- Balance the total charge by adjusting the number of ions needed.
- Write the formula, ensuring that the subscripts show the correct ratio of ions to neutralize the charges.
For example:
- For potassium permanganate (KMnO₄), potassium (K) has a +1 charge, and the permanganate ion (MnO₄⁻) has a -1 charge. Since the charges are equal and opposite, the formula is KMnO₄.
- For calcium phosphate (Ca₃(PO₄)₂), calcium (Ca²⁺) has a +2 charge, and phosphate (PO₄³⁻) has a -3 charge. To balance the charges, you need three calcium ions and two phosphate ions, giving the formula Ca₃(PO₄)₂.
Summary
For lithium chromate, the formula is Li₂CrO₄. The method involves balancing the charges of the ions, adjusting their quantities so that the total charge equals zero. This approach can be used for various ionic compounds, ensuring their formulas are correct based on their charges.
