Task: Question Generation
Input (English): Background Paragraph: For example, if a solid pellet of NaOH is placed into a chamber of HCl gas, a relatively slow acid-base reaction will occur between gaseous HCl molecules and hydroxide ions on the surface of the pellet. If we were to grind the pellet into smaller pieces, it would greatly increase the total surface area, and therefore the overall reaction rate. Once ground up, many hydroxide ions that were on the interior of the pellet, where they were not exposed to any HCl molecules, will now be on the surface, where the necessary collisions can occur. 
Story: In his chemistry lab David is experimenting with how NaOH and HCl gas reacts with each other. He conducted two experiments, experiment A and experiment B. In experiment A he used solid pellets of NaOH, but in experiment B he used ground NaOH. He was surprised to see the difference it made in his experiment.
Output (English): In which experiment the interior hydorxide ion would not be exposed?