GENCHEM do not provide quizzes at all. As can be seen
from Table 3, most of the courses provide at least six tasks
per target topic. NORTON provides about nine although
only two are devoted to dilution. GENCHEM and OLI
provide supported tasks (tutorials2) that present new data
each time the task is opened. However, these tutorials
basically consist of procedural practice with either no, or
an unchanging, cover story.