a 250 g sample is composed of 150 g of sodium (na) and 100 g of chlorine (cl). what is the percent by mass…

Explanation:

Step1: Recall the formula for mass - percent

The formula for mass - percent of a component in a sample is (\text{Mass}%=\frac{\text{Mass of component}}{\text{Mass of sample}}\times100%)

Step2: Identify the values

The mass of (Cl) (component) (m = 100\space g), and the mass of the sample (M=250\space g)

Step3: Substitute the values into the formula

(\text{Mass}%=\frac{100}{250}\times 100%=\frac{100\times100%}{250}) [ \begin{align*} \frac{100\times100%}{250}&=\frac{10000%}{250}\ & = 40% \end{align*} ]

Answer:

(40%) (the fourth option)