Is that ok?

Thank you Mister. Would you please explain me why don't we use is it ok here?

The difference between 'is that ok' and 'is it ok' appears to be an extra consonant /th/ and a vowel difference. However, /th/ gets assimilated with /z/ of 'is' in speech, so you end up with a vowel difference: a closer vowel /?/ and an opener vowel /æ/. No one notices that difference in speech unless you are emphasing the word 'that'.

raindoctorNo one notices that difference in speech unless you are emphasing the word 'that'

However, 'that' is the only natural word choice there.

My idea is to learn it vs that difference here. So I would welcome all answers that clear my doubts.

thanks

'It' is a personal pronoun, referring as expected to the nearest previous noun, 'number'. But that is not what you mean; you wish to refer to the entire clause ('I'll call you at your number'). That statement is why you use 'that'.

I found the following sentencehttp://www.talkenglish.com/LessonDetails.aspx?ALID=479' ("") and agian it made me confused.would you pls explain me why is 'that' used there instead of it?

I would appreciate your reply.

vts nair 'Will it be ok if I call you back in about 30 minutes? '

I'm not sure I've understood your question, but in that case the "it" is just an 'introductory' pronoun used as a provisional subject and it doesn't really refer to anything.

vts nairI found the following sentence 'Will it be ok if I call you back in about 30 minutes? ' ... and again it made me confused.

Here is your choice.

1 I'll call you back in 30 minutes. Will that be OK? (that = the plan I just proposed in the previous sentence)
2 Will it be OK if I cal