Cyanocobalamin, vitamin B12, has the formula C₆₃H₈₈CoN₁₄O₁₄P and a molar mass of 1355.37 g/mol…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Cyanocobalamin, vitamin B12, has the formula and a molar mass of . The molar mass of cobalt is . A tablet holds of the vitamin. Find the percentage of cobalt by mass, the mass of cobalt in the tablet, and the amount of the vitamin in the tablet, in micromoles.
Need a reminder? The key ideaShow
Fat-soluble vitamins (A, D, E, K) are stored in the body. Water-soluble vitamins (B group and C) are not, except B12. Vitamin B12 contains cobalt. Vitamin C reacts with iodine in a 1 : 1 ratio: . The mass fraction of an element in a compound is .
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. One cobalt atom per molecule, so the mass fraction is .
Step 1. Percentage. , which is .
Step 2. Mass of cobalt. micrograms.
Step 3. Amount. micromoles.
Answer: cobalt, micrograms of cobalt and micromoles of vitamin B12.
Check. The amount of cobalt, micromoles micrograms, agrees with step 2.
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