Question

What are the differences between questions with BA (吧) and MA (嗎)?

Answer 1

Although questions with BA (吧) and MA (嗎) both indicate that the speaker has made an assumption of the situation and has an expectation as to what the answer will be, 吧 shows a stronger assumption or expectation than 嗎.

你是學法文的吧？

nǐ shì xué fǎ wén dí ba?

You must be studying French, aren't you? (Near certainty.)

你是學法文的嗎？

nǐ shì xué fǎ wén dí ma?

Are you studying French? (Expecting "yes" to be the answer.)

Reference: YUFA! A Practical Guide to Mandarin Chinese Grammar

Answer 2

吧是感叹语气   吗是疑问语气

Answer 3

The word "Ba"，express approval, speculation, command, request, etc.

The word "Mo", usually used to express doubt