Transit in Beijing Capital Airport. Singapore-PEK-Ulaanbatar

I will land at PEK at 0530 in the morning Air China from Singapore , and then connecting to another Air China at 0835 to Ulaanbatar Mongolia. Is it enough time to change the flights? Do i need to do immigration process if i dont want to exit airport as start and destination are both foreign countries? Also for indian national does visa-free transit apply for the 3 hr 5 min transit period?