What will be the effect on the amount of gas produced if the experiment is repeated using 0.35g of k?

Hello there, I believe you are practicing for the AP Chemistry exam. If you are, so am I :) 

Anyways, the answer is that some gas will be produced but less than the amount of gas produced by Li.

To understand this, we first need to look at the number of moles we have of each substance. For 0.35 grams of Li, we have an estimated value (I am estimating because the multiple choice of the exam is non calculator) of 0.05 moles. For K however, we have an estimated value of 0.01 moles used.

Now look at the two equations: 2K +3H2O ---> 2H2 + 2K(OH)
                                                  2Li +3H2o ---> 2H2 +2Li(OH)
In the question, it specifies that H2 gas is produced as a product. Because both equations produce H2 in a 2:2  ratio (or a simplified ratio of 1:1), 0.05 moles of H2 will be produced for the Li equation, while 0.01 moles of H2 will be produced for the K equation. Therefore, the Li produces more moles of gas than K. 

I hope that makes sense. Happy studying :)

The answer is letter c