Question

a sample of an unknown pure substance x is analyzed and found to contain 7.94 g of element e1, 9.06 g of element e2, and no other elements. a similar analysis is made of three other substances that also only contain elements e1 and e2. the results are shown in the table below. decide whether each substance is a pure substance. if you dont have enough information to decide, choose cant decide.

substance	mass of e1	mass of e2	pure substance?
b	19.1 g	18.9 g	pure substance ( ) mixture ( ) cant decide ( )
c	12.5 g	16.5 g	pure substance ( ) mixture ( ) cant decide ( )

Explanation:

Step1: Recall the law of definite proportions

In a pure substance, the ratio of the masses of its constituent elements is always the same. For a mixture, this ratio can vary.

Step2: Calculate the mass - ratio for each substance

For substance A:
The ratio of mass of \(E_1\) to mass of \(E_2\) is \(\frac{14.6}{8.36}\approx1.75\)
For substance B:
The ratio of mass of \(E_1\) to mass of \(E_2\) is \(\frac{19.1}{18.9}\approx1.01\)
For substance C:
The ratio of mass of \(E_1\) to mass of \(E_2\) is \(\frac{12.5}{16.5}\approx0.76\)
Since the mass - ratios of the elements in substances B and C are different from that in substance A, and the mass - ratio within each substance is not consistent with others, these are mixtures.

Answer:

A. mixture
B. mixture
C. mixture