Final answer:
To find the number of millimoles of potassium ion contained in 20 grams of potassium bicarbonate (KHCO3), convert the mass of KHCO3 to moles and then to millimoles. There are 0.2 moles of potassium ion in 20 grams of KHCO3, which is equivalent to 200 millimoles. Therefore, the correct option is A.
Step-by-step explanation:
To find the number of millimoles of potassium ion contained in 20 grams of potassium bicarbonate (KHCO3), we need to convert the mass of KHCO3 to moles and then to millimoles. The molecular weight (MW) of KHCO3 is 100 g/mol, so 20 grams is equal to 0.2 moles. Since there is one mole of potassium ion (K+) in one mole of KHCO3, we can say that there are 0.2 moles of potassium ion in 20 grams of KHCO3. To convert moles to millimoles, we multiply by 1000, giving us 200 millimoles. Rounded to the nearest whole number, the answer is 200 millimoles, so the correct option is A. 2.