Question

In an experiment, a $2.514{\text{ }}g$ sample of calcium is heated in oxygen and the compound formed has a mass of$3.518{\text{ }}g$ . What is the empirical formula for the compound?

Answer 1

In chemistry, the periodic table plays an important role. In the periodic table there are totally $118$ elements. In the periodic table there are totally $18$ columns and $7$ rows. The columns are called groups. Hence, $18$ groups in the periodic table. The rows are called a period. Hence, totally $7$ period in the table. Oxygen is one of the elements in the periodic table. The symbol of oxygen is ${\text{O}}$ .Oxygen is one of the sixteenth groups in the periodic table. The atomic number of Oxygen is $8$ . The mass number of Oxygen is $16$ . The valency of Oxygen is $2$ . The stable oxidation state of Oxygen is $- 2$ . The atomic number of the element is nothing but the number of electrons or the number of protons. The mass number of the atom is the sum of the number of protons and the number of neutrons.
Formula to be used:
Moles are defined as the given mass of the molecule is divided by the molecular mass of the molecule.
$moles\, = \dfrac{{mass\,of\,the\,molecule}}{{molecular\,weight\,of\,the\,molecule}}$
The molecular weight of the molecule depends on the atomic weight of the atom present in the molecule. The molecular weight of the molecule is equal to the sum of the molecular weight of the atom and the number of the respective atoms in the molecule.

Complete answer:
The atomic weight of calcium is $40.1$ .
The atomic weight of oxygen is $16$ .
The weight of the calcium atom in the sample is $2.514{\text{ }}g$ .
The weight of calcium oxide in the sample is $3.518{\text{ }}g$ .
The weight of the oxygen atom in the sample

$$= 3.518{\text{ - }}2.514{\text{ }} \\\ = 1.004 \\\$$

The moles of the calcium atom is calculated as,

$moles\, = \dfrac{{mass\,of\,the\,molecule}}{{molecular\,weight\,of\,the\,molecule}}$

$$moles\, = \dfrac{{2.514{\text{ }}g}}{{40.1}} \\\ = 0.0627moles \\\$$

The moles of the oxygen atom is calculated as,

$moles\, = \dfrac{{mass\,of\,the\,molecule}}{{molecular\,weight\,of\,the\,molecule}}$

$$moles\, = \dfrac{{1.0g}}{{16}} \\\ = 0.0627moles \\\$$

Both the moles are the same, with an equal number of moles of calcium and oxygen atom present in calcium oxide. So, the empirical formula of calcium oxide is $CaO$ .
According to the above discussion, we conclude in an experiment, a $2.514{\text{ }}g$ sample of calcium is heated in oxygen and the compound formed has a mass of $3.518{\text{ }}g$ . The empirical formula for the compound is $CaO$ .

Note:
Oxides of alkaline elements are soluble in water. Alkaline elements are the first group elements in the periodic table. Oxide of alkaline earth elements is partially soluble in water.Alkaline earth elements are the second group of elements in the periodic table. The oxidation reaction means the addition of oxygen or the removal of hydrogen or the loss of electrons in the reaction from reactant to product. Compared to metal, metal oxide is highly stable. The formula of a chemical compound having one oxygen atom and another atom is called oxide. Oxygen is dianion because the oxidation state of Oxygen is $- 2$ .