On a day when promotion rivals QPR, Swansea and Norwich all won it was crucial the Bluebirds kept up with the pace in the battle to win promotion to the Barclays Premier League.
Points matter more than performances at this stage in the season and Chopra looked to have produced the only moment of inspiration to head home Craig Bellamy's cross after 65 minutes.
That was until on-loan Arsenal forward Emmanuel-Thomas made the points safe with a stunning effort out of nothing in injury time.
They were only the ninth and 10th league goals conceded by Hull at the KC Stadium this term and ended the home side's nine-match unbeaten run, while Cardiff have now lost just one of their last 10.
Source: PA
Source: PA