Excellent idea! Although it appears a few things aren't working properly. The 'O' for capital didn't appear when I typed in Ottawa, but did when I typed in Oman. Also it didn't accept Kelvin as an answer
Please add oganesson (Og, 118th element) for O. Kilogram doesn't work for me either. By the way, I think you should use a spreadsheet to list all your possible answers, and then import in later. This way, you will less likely to miss any type-ins, especially with this type of quizzes that can confuse you.
I don't think kilogram itself is the scientific unit. I believe it's just gram. kilo meaning that there is a thousand grams, Example: Milligram, Centigram. Same goes for ounces and meters if you want to include those as scientific units.
linguistically, it would make sense for grams to be the base unit. However, kilogram has been defined as the SI base unit - you can read more about it HERE, HERE or on some other site, there's plenty. I'm not an expert on this but ounces are a British thing that isn't universally acknowledged as a base unit. I'm afraid I cannot accept every specific unit/name, because that would be impossible - there's too many. I'll have to stick to the SI base units, sorry. But thank you for your comment!
Great quiz! - Missed most, except for the countries and capitals. Shuld have gotten the oscar winners, but was concentrating too much on the elements. Practice... practice...practice!