Fluorine-18 is a radioactive isotope of the element fluorine. According to Wikipedia, its half-life is 109.771 minutes, which means the amount present is halved every 109.771 minutes.
You can use the formula for half-life, such that
. You begin with 135 mg fluorine-18. We don't even need to plug in to the formula to see that after 110 min, the amount has halved to equal
67.5 mg.
Well the answer is 207.2. You take the lowest sig figs that you are using which would be 2500= 2 sig figs. 207.2 rounded to 2 sig figs would be 210
3 a <span>positively charged nucleus surrounded by negatively charged protons</span>
Answer:
If you want the first option you need 2.5M.
If you want the second, you will end up with 120ml so your starting solution is:
0.5x (120/20) = 3.0M
This assumes that there’s no loss of volume on mixing. To remove that uncertainty, start with the 20ml of acid and add water, mixing, till you get the right volume.
Answer:
513.975g
Explanation:
I'm assuming that the question has Aluminium and Chlorine as the question is not clear.
1. Balance the equation
2 Al + 3 Cl2 → 2AlCl3
2. Use the mole = mass/mr equation and molar ratio to find the mass of AlCl3
133.5 x 3.85 = 513.975g