Here's how to calculate the grams in 238 moles of arsenic:

1. Find the molar mass of arsenic (As):

* You can find this on the periodic table. The molar mass of arsenic is approximately 74.92 g/mol.

2. Use the following formula:

* Grams = Moles * Molar Mass

3. Calculate:

* Grams = 238 mol * 74.92 g/mol

* Grams = 17,832.56 g

Therefore, there are approximately 17,832.56 grams in 238 moles of arsenic.