Based on the law of definite composition, Dalton proposed that one atom of carbon combines with two atoms of oxygen to always produce CO2.
Similarly,he proposed that two atoms of hydrogen combine with one atom of oxygen to give a molecule of H2O.
Finally,Dalton reasons that two atoms of hydrogen in water could substitue for each of the oxygen atoms in carbon dioxide. This would result in a molecule with one carbon and four hydrogen atoms, that is CH4.
Question:Please help me to understand how he arrives at 'H4'in the formula CH4 (4 hydrogen atoms)when he's substituting two atoms of hydrogen from H20.
Thank You.
Dalton's reasoning behind arriving at 'H4' in the formula CH4 when substituting two hydrogen atoms from H2O is based on the Law of Definite Proportions and the Law of Multiple Proportions.
According to the Law of Definite Proportions, elements combine in definite and fixed proportions to form compounds. Therefore, when hydrogen combines with oxygen to form water (H2O), it always does so in a 2:1 ratio, meaning two hydrogen atoms for every one oxygen atom.
Now, let's consider the combination of carbon and hydrogen in the context of the Law of Multiple Proportions. Dalton proposed that carbon combines with oxygen in a 1:2 ratio to form carbon dioxide (CO2). This means that one atom of carbon combines with two atoms of oxygen.
If we apply similar principles to the substitution of hydrogen atoms in carbon dioxide, we can see that carbon dioxide originally has two oxygen atoms. Dalton suggests that instead of these two oxygen atoms, we can substitute them with two hydrogen atoms from water (H2O).
Since water has a 2:1 ratio of hydrogen to oxygen, taking two hydrogen atoms will give us a total of four hydrogen atoms (2 hydrogen atoms × 2). Therefore, when two atoms of hydrogen from water substitute for each oxygen atom in carbon dioxide, we end up with the formula CH4, which represents one carbon atom and four hydrogen atoms.
In summary, Dalton's reasoning is based on the fixed proportions of elements in compounds (Law of Definite Proportions) and the ability to substitute atoms while maintaining those proportions (Law of Multiple Proportions). By substituting two hydrogen atoms from water for each oxygen atom in carbon dioxide, he arrived at CH4, which represents one carbon atom and four hydrogen atoms.