What are the species X and Y in the following`X+H_(2)OtoH_(2)Cr_(2)O_(7)overset(OH^(-))toY`

Options

A. `CrO_(4)^(-2),Cr_(2)O_(7)^(-2)`
B. `CrO_(3),Cr_(2)O_(3)`
C. `H_(2)CrO_(4),H_(2)Cr_(2)O_(7)`
D. `CrO_(3),CrO_(4)^(-2)`

Answer

To solve the problem, we need to identify the species X and Y based on the given reaction. Let's break down the steps:

### Step 1: Identify the reaction
The reaction given is:
\[ X + H_2O \to H_2Cr_2O_7 \]
This indicates that species X reacts with water to form dichromic acid (H2Cr2O7).

### Step 2: Determine species X
Dichromic acid (H2Cr2O7) can be formed from chromium trioxide (CrO3) when it reacts with water. The balanced equation for this reaction is:
\[ CrO_3 + H_2O \to H_2Cr_2O_7 \]
Thus, we can conclude that:
\[ X = CrO_3 \]

### Step 3: Identify the second part of the reaction
Next, we look at the second part of the reaction:
\[ H_2Cr_2O_7 \overset{(OH^-)} \to Y \]
This indicates that in the presence of hydroxide ions (OH^-), H2Cr2O7 will convert to another species Y.

### Step 4: Determine species Y
In a basic medium, dichromic acid (H2Cr2O7) converts to chromate ion (CrO4^2-). The balanced equation for this transformation is:
\[ H_2Cr_2O_7 + 2OH^- \to 2CrO_4^{2-} + 2H_2O \]
Thus, we can conclude that:
\[ Y = CrO_4^{2-} \]

### Final Answer
From the analysis:
- Species X is **CrO3** (chromium trioxide).
- Species Y is **CrO4^2-** (chromate ion).

### Summary
- X = CrO3
- Y = CrO4^2-