Achieve Week 2 Questions 9 and 10: Predominant Species Present

[Ciabel Querol 3E]

I just want to make sure my understanding of the topic covered in questions 9 and 10 of the week 2 homework is solid. For question 10, why is the solution more acidic if there is more BH+ in the solution, even though it means that there is more OH- in solution? What is a good method for attacking these sorts of problems?

[Gavin_Yang_1J]

I'm not really sure, I think maybe it is because in the case of question 10, the pH of the solution is less than 7/the pKa even though it is a weak base, meaning that there is extra H+ from somewhere other than the base, which would push the reaction towards the products.