Which has the correct name-formula combination? A) Iron(II) nitride – FeN B) Nickel (II) oxide -NIO2 C) Titanium (IV) phosphide – TiP D) Manganese(II) sulfide – MnS 2. What type of reaction is represented by the following equation: CoCl2(aq) + 2NaOH(aq) → Co(OH)2(s) + 2NaCl(aq) A) acid-base B) decomposition C) precipitation D) redox (oxidation-reduction)
The Correct Answer and Explanation is :
Question 1 Answer: A) Iron(II) nitride – FeN
Explanation:
In this question, we need to match the correct name to the chemical formula of a compound. To do so, we must first understand the oxidation states of the metals in each option and whether they match the chemical formula.
A) Iron(II) nitride – FeN:
- Iron (Fe) can have different oxidation states, such as +2 or +3. In this case, the “Iron(II)” indicates an oxidation state of +2.
- Nitride (N³⁻) is the ion formed by nitrogen when it gains three electrons, giving it a charge of -3.
- To balance the charges, you need one Fe²⁺ ion to pair with one N³⁻ ion, resulting in FeN, which is indeed correct.
B) Nickel(II) oxide – NiO2:
- Nickel (Ni) in the “Nickel(II)” form means it has an oxidation state of +2.
- However, oxide (O²⁻) has an oxidation state of -2. So, for a balanced compound, the correct formula should be NiO (not NiO2).
C) Titanium(IV) phosphide – TiP:
- Titanium (Ti) with the oxidation state of +4 will form a compound with phosphide (P³⁻), which requires balancing. The correct formula for this compound should be Ti₃P₄, not TiP.
D) Manganese(II) sulfide – MnS:
- Manganese (Mn) in the +2 oxidation state would combine with sulfide (S²⁻) to form MnS, which is indeed a valid compound, but the correct formula is not needed for this question as option A is correct.
Question 2 Answer: C) Precipitation
Explanation:
The given reaction is:
[ \text{CoCl}_2(aq) + 2\text{NaOH}(aq) \rightarrow \text{Co(OH)}_2(s) + 2\text{NaCl}(aq) ]
- CoCl₂ and NaOH are both aqueous solutions, meaning they are dissolved in water. The reaction forms Co(OH)₂, which is a solid precipitate (as indicated by “(s)”).
- Precipitation reactions occur when two aqueous solutions react to form a solid product, which is what happens here with Co(OH)₂. Therefore, the correct answer is C) Precipitation.