Reading tone
FoundationThey are different questions and are answered from different evidence. The two question types share a passage and are answered from different evidence — tone from the writer's word choices, purpose from the passage's structure. Confusing them produces an answer that is true about one and asked about the other.
A passage can be critical in tone and informative in purpose.
attitude and intent are independent
A critical passage must be trying to persuade.
tone read as purpose
Where it bites
Where the options for a purpose question are all adjectives, or the options for a tone question are all infinitives. The parts of speech tell you which is being asked.