Dominant 7th chord fingerings for piano

Your fingering makes no b.com/tag/sense">sense to me. However, fingering in an exam situation is not something the examiner will be looking at. Fingering in the syllabus books is only a b.com/tag/suggestion">suggestion, although it usually turns out to be the best option for most folks. S/he only wants to hear correct, regularly played notes, so how you finger them is how you are most comfortable. Dominant 7th of C maj. could be C E G Bb, with the one black b.com/tag/key">key, or could be construed as G B D F, with none. If the former, then Bb can be played with a thumb. It's usually best not to use thumb on black b.com/tag/key">keys, when there's an alternative, as it's the shortest b.com/tag/digit">digit, and puts the hand further from the player, but as any alternative is not as good, use the thumb. Seems quite late to be considering this, with an exam a week away!