Just applied for my first Chase card (Sapphire Preferred) and got instant approval. Then, I logged into my United account and saw the 50k miles offer from Chase, so I figured I should go for it and applied online. Got the "you will hear back soon" message, so I am assuming a deny.

Is there anything I can do to improve my chances before actually receiving the letter in the mail (said 30 days to hear back)? Is there a number to call where I can see if they'll spread the credit limit between the two cards?

Is it normal to get rejected on the 2nd card since I applied for both back to back?