The spectrometer in AAS can be either single-beam or double-beam. Give one major difference between them. State the major function of the transducer in a mass spectrometer. Use the stick diagram to il

2-methylbutane has the formula $C_5H_{12}$. Its structure is:

When ionized, it forms a molecular ion $C_5H_{12}^+$. Fragmentation occurs at various C-C bonds.

• Loss of $CH_3$ (methyl group, $m/e=15$): $C_4H_9^+$ ($m/e=57$)
• Loss of $C_2H_5$ (ethyl group, $m/e=29$): $C_3H_7^+$ ($m/e=43$)
• Loss of $C_3H_7$ (propyl group, $m/e=43$): $C_2H_5^+$ ($m/e=29$)
• Loss of $C_4H_9$ (butyl group, $m/e=57$): $CH_3^+$ ($m/e=15$)

The provided data (15, 14, 13, 12) are for very small fragments, likely from further breakdown of the initial fragments.

• $m/e = 15$: $CH_3^+$
• $m/e = 14$: $CH_2^+$
• $m/e = 13$: $CH^+$
• $m/e = 12$: $C^+$

A stick diagram plots relative intensity against mass-to-charge ratio ($m/e$).

• At $m/e = 15$, Relative Intensity = 100
• At $m/e = 14$, Relative Intensity = 75
• At $m/e = 13$, Relative Intensity = 50
• At $m/e = 12$, Relative Intensity = 22

The graph would have:

• X-axis: Mass-to-charge (m/e)
• Y-axis: Relative Intensity (%)
• Vertical lines (sticks) at $m/e$ values 12, 13, 14, 15, with heights corresponding to their relative intensities (22, 50, 75, 100 respectively).

Relative Intensity (%)
^
|   100 |       |       |   X
|    75 |       |   X   |
|    50 |   X   |       |
|    25 | X     |       |
|     0 +---------------------> m/e
        12  13  14  15

(Note: This is a textual representation of the stick diagram. In a proper diagram, the 'X' marks would be the top of vertical lines extending from the x-axis.)

4 (c) (ii) At what m/e value is the base peak?
The base peak is the most intense peak in the mass spectrum, assigned a relative intensity of 100%.
From the given data:

• Relative intensity 100 corresponds to $m/e = 15$.

The base peak is at $\boxed{m/e = 15}$.