I have no idea what I'm doing wrong here...

0.435 g CaCl2 looks ok to me. Are you keying the answer into an on-line data base? If so, I notice you have only 1 place in the 0.3% (unless you just omitted the 0 as in 0.300%) and that may be too many significant figures. I would go with 0.4 g CaCl2 as the answer. Let me know how this turns out.

Dr.Bob222 -

You are absolutely right. It totally slipped my mind that 0.3 has ONE sigfig. Thank you.. your help is much appreciated!

In your solution, you used the formula "0.3g / 100g" to calculate the mass of calcium chloride in the solution. The mistake you made is that you used the wrong percentage value in the calculation.

0.3% represents 0.3 parts out of 100 parts, so the correct calculation should be:

145g x (0.3 / 100) = 0.435g

Therefore, your calculation of 0.435g is correct, and you correctly rounded it to 0.44g CaCl2.

In summary, to solve the problem correctly, you should use the percentage as a decimal (0.3 divided by 100), not as a unit (0.3 grams per 100 grams).