a 400. g sample is composed of 100. g of cesium (cs) and 300. g of iodine (i). what is the percent by mass…

Explanation:

Step1: Identify mass of iodine and total mass

Mass of iodine ($m_{I}$) = 300 g, total mass ($m_{total}$) = 400 g.

Step2: Use percent - by - mass formula

Percent by mass of iodine = $\frac{m_{I}}{m_{total}}\times100%=\frac{300}{400}\times100%$.

Step3: Calculate the result

$\frac{300}{400}\times100% = 75.0%$.

Answer:

75.0%