Analysis of 20.0 g of a compound containing only calcium and bromine indicates that 4.00 g of calcium are present. what is the empirical formula of the compound formed?
a. ca7br2
b. ca3br2
c. cabr2
d. ca5br2

d.

Explanation:

Mass of calcium = 4.00 g

Molar mass of calcium = 40.078 g/mol

Moles of calcium = 4.00 / 40.078 moles = 0.9981 moles

Given that the compound only contains calcium and bromine. So,

Mass of bromine in the sample = Total mass - Mass of calcium

Mass of the sample = 20.0 g

Mass of bromine in sample = 20.0 - 4.00 g = 16.0 g

Molar mass of bromine = 79.904 g/mol

Moles of Bromine  = 16.0 / 79.904  = 0.2002 moles

Taking the simplest ratio for Ca and Br as:

0.9981 : 0.2002  = 5 : 1

The empirical formula is =

the answer for sodium is 0.186

the answer for rubidium is 0.251

answer by yourhope:

how do models compare to real-world objects?

d. most models represent a real-world object in a simpler way.

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