Two experiments were conducted: 4.125 g of copper(II) oxide, CuO2, was reduced by heating at high pressure with excess hydrogen to yield 3.294 g of copper Cu. 1.179 g of copper Cu was dissolved in nitric acid to yield copper(II) nitrate, which was converted to 1.476 g copper(II) oxide, CuO2, on ignition. Show that the results illustrate the law of definite proportions by calculating the percentage of oxygen in copper(II) oxide in experiments 1 and 2.

Explanation:

4.125 g of copper oxide contains 3.294 g of Cu . Rest is oxygen

oxygen is 4.125 - 3.294 = .831 g

Ratio of oxygen and copper = .831 : 3.294

.831 / .831 : 3.294 / .831

= 1 : 3.96

1 : 4 ( Approx )

percentage of oxygen in copper oxide = 20 % approx

in the second experiment ,

1.476 g of copper oxide is formed from 1.179 g of Cu

oxygen in this copper oxide = 1.476 - 1.179 = .297 g

Ratio of oxygen and copper

.297 : 1.179

.297/.297 : 1.179/ .297

1 : 3.96

1 : 4 ( approx )

percentage of oxygen in copper oxide = 20 % approx

So it follows the law of definite proportions .

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.