Understanding the Terms:

* ppm (parts per million): A way to express very low concentrations. 100 ppm means 100 parts of methanol per 1 million parts of the solution.

* Solution: A mixture of two or more substances, in this case, methanol and water.

Calculation:

1. Convert ppm to mg/L:

* 1 ppm = 1 mg/L (milligram per liter)

* 100 ppm = 100 mg/L

2. Convert mL to L:

* 100 mL = 0.1 L

3. Calculate the mass of methanol needed:

* Use the formula: mass (mg) = concentration (mg/L) * volume (L)

* mass (mg) = 100 mg/L * 0.1 L = 10 mg

Therefore, you need 10 mg of methanol to make a 100 ppm solution in 100 mL of water.

Important Notes:

* Methanol is toxic: Always handle methanol with extreme care and use appropriate safety precautions.

* Precision: This calculation assumes a standard density of water. For highly accurate results, you may need to account for the density of your specific water.

* Solubility: Ensure that the calculated amount of methanol is within its solubility limit in water.

If you are working with methanol, please consult a safety data sheet (SDS) for handling guidelines and potential risks.