Thyroxine is a hormone secreted by the thyroid gland and has a formula of C15H11NO4I4. How many grams of iodine are there in a 5g sample of thyroxine?
This question is an application of ratios using the molecular mass of thyroxine and that of iodine.
The chemical formula of thyroxine is given as C15H11NO4I4. The molecular mass of thyroxine is 12*15 + 1*11 + 14 + 16*4 + 127*4 = 777.
777 g of thyroxine has 127*4 = 508 g of iodine.
In 5 g of iodine there are (5/777)*508 = 3.268 g of iodine.
There are 3.268 g of iodine in 5 g of thyroxine.