Question

Empirical formula of a compound if a 50.0 g sample of it contains 9.1g Na ,20.6 g Cr ,and 22.2 g O

Answer 1

Answer:

The empirical formula of a compound is Na2Cr2O7

Explanation:

Empirical formula is defined as the lowest ratio of elements present in any substance. In order to determine the empirical formula for a substance containing these elements we have to follow some steps.

1.In the first step, we have to divide the given mass of an element with its molecular mass to convert the mass to moles.

$No. of moles of Na=Given Mass of Na/Molecular Mass of Na=9.1/23=0.396$

Similarly, the moles of Cr and O in that compound were calculated and found as 0.396 and 1.3875, respectively.

2. Then the next step is to determine the lowest moles and divide all the moles with that lowest mole. As here the lowest mole is 0.396. So on dividing the moles of Na, Cr and O with 0.396, we will obtain the ratio as 1:1:3.5.

3. As the ratio consists of a fractional number, we have to multiply it with the smallest possible integer to convert it to whole number. In this case, if we multiply it with 2 , we will get the ratio as 2:2:7.

Thus, the empirical formula for the compound can be written as Na2Cr2O7.