Absolutely, let's break this down step by step! --- ## Understanding the Problem The question provides an Electrospray Ionization Mass Spectrum (ESI-MS) for an unknown compound. You are asked to **determine the molecular weight** of the compound using the spectrum. --- ## Reading the Spectrum - The x-axis is **m/z** (mass-to-charge ratio). - The y-axis is relative **abundance** (intensity). - Main peaks are at: - **67.7** - **100.1** - **200.1** --- ## Key Concept in ESI-MS - ESI-MS often produces **multiply charged ions**. - Peaks arise from ions with different charge states (**z**). - The **m/z value** is calculated as: \[ \frac{M + nH}{n} \] - \( M \): molecular weight of the compound - \( n \): number of charges (protons added) - \( H \): mass of a proton (\(\approx 1\) Da) --- ## Assigning Peaks Let's look at the three peaks: 1. **200.1**: Often, the largest m/z is the singly charged ion (\( n = 1 \)): \[ \frac{M + 1}{1} = M + 1 \] \[ M = 200.1 - 1 = 199.1 \] 2. **100.1**: Likely a doubly charged ion (\( n = 2 \)): \[ \frac{M + 2}{2} = 100.1 \] \[ M + 2 = 200.2 \implies M = 198.2 \] (Very close to above) 3. **67.7**: Triply charged ion (\( n = 3 \)): \[ \frac{M + 3}{3} = 67.7 \] \[ M + 3 = 203.1 \implies M = 200.1 \] --- ## Calculating the **Molecular Weight** There are slight differences due to rounding and instrument calibration, but they all suggest: \[ \boxed{M \approx 199} \] So, **the molecular weight of the compound is approximately 199 Da (Daltons)**. --- ## **Summary Table** | m/z | z (charge) | Formula | Calculated M | |-------|------------|-------------------|--------------| | 200.1 | 1 | \( M + 1 = 200.1 \) | 199.1 | | 100.1 | 2 | \( (M+2)/2 = 100.1 \) | 198.2 | | 67.7 | 3 | \( (M+3)/3 = 67.7 \) | 200.1 | --- ## **Key Takeaway** - In ESI-MS, look for peaks that are separated by the charge difference. - Use the equation \( m/z = (M+n)/n \) to solve for \( M \). - **The molecular weight of the compound is about 199 Da.** Let me know if you’d like more details or a deeper explanation!