I find trello much quicker to use than google sheets for structuring study topics, it's easier to insert images and the markup is quick. You could structure it as follows:
One board per subject e.g. Organic chemistry
One list per subtopic e.g. Acids
One card with questions in the description pr topic, e.g. pH
One card with answers.
So you go down the list of questions and press J to go to the next card with answers, mark any cards you had no problems answering green, yellow or red if you couldn't answer. This gives you a visual overview over what you still need to study.
Is there any way to place the answers in the same card as the questions without immediately showing them?