To calculate the weight of 5.0 moles of lithium in grams, we need to know the molar mass of lithium. The molar mass of lithium is 6.941 g/mol. This means that 1 mole of lithium weighs 6.941 grams.

Therefore, 5.0 moles of lithium will weigh:

$$5.0 \text{ moles Li} \times \frac{6.941 \text{ g Li}}{1 \text{ mole Li}} = 34.705 \text{ g Li}$$

So, 5.0 moles of lithium would weigh 34.705 grams.