Formula and equations Flashcards
Write a balanced equation, with state symbols for this statement:
When chlorine gas is bubbled into an aqueous solution of potassium iodide, iodine (I2) appears as a black solid suspended in potassium chloride solution.
2Cl(g) + 2KI (aq) –> I2 (s) + 2KCl (aq)
Take note that it is not 2KI2 for (aq) and also not I for the (s) because:
Chemical Formula of Potassium Iodide (KI):
Charge Balance:
Potassium (K) is a Group 1 metal with a +1 charge (K⁺).
Iodine (I) is a Group 17 halogen with a -1 charge (I⁻).
To form a neutral compound, one K⁺ ion pairs with one I⁻ ion:
Formula: KI (1:1 ratio)
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Formula: KI (1:1 ratio).
Why Not KI₂?
KI₂ would imply two I⁻ ions (-2 total charge) paired with one K⁺ ion (+1 charge), resulting in a net charge of -1.
This violates the rule of charge neutrality in ionic compounds.
Chemical Formula for Iodine (I₂):
Elemental Iodine:
Exists as diatomic molecules (I₂) in its pure form (like other halogens: Cl₂, Br₂).
Iodide Ion:
When iodine gains an electron (e.g., in ionic compounds like KI), it becomes I⁻.
Key Takeaways:
Ionic Compounds (e.g., KI):
Formed by transfer of electrons.
Formula reflects charge balance (K⁺ + I⁻ → KI).
Molecular Elements (e.g., I₂):
Exist as diatomic molecules in their pure state.
Common Mistake to Avoid:
Confusing elemental iodine (I₂) with the iodide ion (I⁻) in compounds.
KI contains iodide ions (I⁻), not elemental iodine (I₂).
Final Answer:
Potassium iodide: KI (not KI₂).
Elemental iodine: I₂.
Write a balanced equation, with state symbols for this statement:
Copper powder reacts with hot nitric acid to form copper (II) nitrate and water, and also releases the brown gas, nitrogen dioxide.
