Question

Question 1
Hydrogen selenide (H2Se) reacts with water according to the following equation.

H2Se + H2O → SeH– + H3O+

Identify the acid, base, conjugate acid, and conjugate base in this reaction

(2 points)
Acid Base Conjugate acid Conjugate base
H2Se




H3O+




Question 2
Use the periodic table to complete the next two questions.

An illustration shows the periodic table of elements with elements arranged in increasing order of atomic number in 18 columns (groups) and 7 rows (periods). The electronegativity of elements increases from left to right, across a period. The hydrogen on the left is included in group with medium electronegativity. Also, fluorine is shown as element with highest electronegativity.

Look at Selenium (Se) and Oxygen (O) on the Periodic Table which one is larger? (1 point)
Responses

Oxygen (O)
Oxygen (O)

Selenium (Se)
Selenium (Se)

They are both the same size
They are both the same size
Question 3
Which element is more capable of holding a negative charge?(1 point)
Responses

Oxygen (O)
Oxygen (O)

Selenium (Se)
Selenium (Se)
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Answer 1

**Question 1:**

In the reaction \( \text{H}_2\text{Se} + \text{H}_2\text{O} \rightarrow \text{SeH}^- + \text{H}_3\text{O}^+ \), we can identify the following:

- **Acid:** H₂Se (it donates a proton, H⁺)
- **Base:** H₂O (it accepts a proton)
- **Conjugate Acid:** H₃O⁺ (the species formed when water accepts a proton)
- **Conjugate Base:** SeH⁻ (the species formed when H₂Se donates a proton)

So the completed table is:

| Acid | Base | Conjugate Acid | Conjugate Base |
|----------|-------|----------------|-----------------|
| H₂Se | H₂O | H₃O⁺ | SeH⁻ |

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**Question 2:**

In comparing Selenium (Se) and Oxygen (O):

- **Selenium (Se)** is larger than **Oxygen (O)**. This is because Se is in Period 4, while O is in Period 2, and elements generally increase in size down a group in the periodic table.

So the answer is:

- **Selenium (Se)**

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**Question 3:**

Among the two elements, **Oxygen (O)** is more capable of holding a negative charge compared to **Selenium (Se)**. This is due to Oxygen's higher electronegativity and its smaller atomic radius, which allows it to stabilize a negative charge more effectively.

So the answer is:

- **Oxygen (O)**