Question

determine the name for each of the ionic compounds from their formulas. cas: calcium sulfide correct answer au₂o₃: gold (iii) oxide incorrect answer k₂co₃: potassium carbonate correct answer nipo₄: nickel(iii) phosphate incorrect answer

Explanation:

For $\boldsymbol{\ce{Au2O3}}$:

Step1: Identify ions

Gold ion: In $\ce{Au2O3}$, let oxidation state of $\ce{Au}$ be $x$. Oxygen is $-2$. So $2x + 3(-2)=0\implies 2x = 6\implies x = +3$. So $\ce{Au^{3+}}$ (gold(III) ion) and $\ce{O^{2-}}$ (oxide ion).

Step2: Name the compound

Ionic compound naming: cation (with charge if variable) + anion. Gold has variable charge, so use roman numeral. $\ce{Au^{3+}}$ (gold(III)) and $\ce{O^{2-}}$ (oxide). So name is Gold(III) Oxide? Wait, no, wait—wait, actually, $\ce{Au2O3}$ is named Gold(III) Oxide, but maybe the system has a typo? Wait, no, maybe I made a mistake. Wait, no, gold(III) oxide formula is $\ce{Au2O3}$. Wait, maybe the original answer was marked incorrect by mistake? Or maybe the question expects "Aurium(III) Oxide" but no, standard is Gold(III) Oxide. Wait, maybe the problem is with $\ce{NiPO4}$:

For $\boldsymbol{\ce{NiPO4}}$:

Step1: Identify ions

Phosphate is $\ce{PO4^{3-}}$. Let nickel's oxidation state be $x$. So $x + (-3)=0\implies x = +3$? Wait, no, $\ce{NiPO4}$: nickel ion and phosphate ion. Wait, nickel can be +2 or +3. Wait, phosphate is $\ce{PO4^{3-}}$. So if formula is $\ce{NiPO4}$, then nickel must be +3? But actually, the correct formula for nickel(III) phosphate should be $\ce{NiPO4}$? Wait, no, nickel(II) phosphate is $\ce{Ni3(PO4)2}$. Wait, let's calculate:

For $\ce{NiPO4}$: charge of $\ce{PO4^{3-}}$ is -3. So nickel's charge: $x + (-3)=0\implies x = +3$. So nickel(III) phosphate. But maybe the error is in the formula? Wait, maybe it's $\ce{Ni3(PO4)2}$ for nickel(II) phosphate. Wait, no, the user's problem has $\ce{NiPO4}$ with incorrect answer as Nickel(III) Phosphate. So let's re - evaluate:

Wait, maybe the formula is wrong, but assuming the formula is $\ce{NiPO4}$, let's do it properly.

Step1: Cation and Anion

Cation: $\ce{Ni^{n+}}$, Anion: $\ce{PO4^{3-}}$.

Step2: Charge Balance

In $\ce{NiPO4}$, the overall charge is zero. So $n + (-3)=0\implies n = +3$. So nickel is in +3 oxidation state.

Step3: Naming

Cation: Nickel(III) (since nickel has variable oxidation states, we use roman numeral for +3), Anion: Phosphate ($\ce{PO4^{3-}}$). So the name should be Nickel(III) Phosphate. But the system says it's incorrect. Maybe the formula is $\ce{Ni3(PO4)2}$ (nickel(II) phosphate), but the given formula is $\ce{NiPO4}$. Maybe a typo.

But back to $\ce{Au2O3}$: The correct name for $\ce{Au2O3}$ is Gold(III) Oxide. Maybe the system's "Incorrect Answer" is a mistake.

For $\ce{NiPO4}$: Let's check again. If the formula is $\ce{NiPO4}$, then nickel is +3, so Nickel(III) Phosphate is correct. But if the intended formula was $\ce{Ni3(PO4)2}$, then it's Nickel(II) Phosphate. Maybe the formula has a typo.

Answer:

s:

• $\ce{Au2O3}$: Gold(III) Oxide (the system's marking as incorrect might be an error)
• $\ce{NiPO4}$: If the formula is correct, Nickel(III) Phosphate; if the formula is $\ce{Ni3(PO4)2}$, Nickel(II) Phosphate (but based on given formula $\ce{NiPO4}$, Nickel(III) Phosphate is correct)

(Note: The first and third compounds are correctly named as per ionic compound naming rules. The second and fourth might have issues due to possible formula or system errors.)