Question

Hydrogen and oxygen always react in a \(1: 8\) ratio by mass to form water. Farly investigators took this to mean that oxygen was eight times more massive than hydrogen. What did these investigators assume about water's chemical formula?

Short answer

Investigators assumed water's formula was HO, implying equal atoms of hydrogen and oxygen.

Step-by-step solution

Understanding Ratio by Mass

The problem states that hydrogen and oxygen react in a 1:8 mass ratio to form water. This indicates that for every 1 gram of hydrogen, 8 grams of oxygen are required in the chemical reaction.

Assuming Relative Mass

Investigators considered this mass ratio and hypothesized that such proportions indicated the relative masses of the hydrogen and oxygen atoms themselves. They thought that because 8 grams of oxygen were required for 1 gram of hydrogen, oxygen must be eight times heavier than hydrogen atomically.

Link to Chemical Formula

The chemical formula of water is actually H₂O, which in modern understanding means each water molecule consists of 2 hydrogen atoms and 1 oxygen atom. However, the assumption of the early investigators likely led them to believe water's formula was HO, suggesting a 1:1 atomic composition where oxygen is indeed eight times heavier.

Key concepts

Mass Ratio

In chemistry, a mass ratio is a way to express the relative amounts of different elements in a chemical compound. For water production, the mass ratio of hydrogen to oxygen is famously 1:8. This implies that for every 1 gram of hydrogen, you need 8 grams of oxygen in the reaction to form water. This mass ratio helps chemists understand the proportion in which elements combine or react. It tells us about the stoichiometry of a chemical reaction, ensuring that the atoms balance correctly when forming new compounds. This concept is crucial for forming overlying theories in chemical bonding and compound formation.

Hydrogen

Hydrogen is the lightest and most abundant element in the universe. Its atomic mass is approximately 1 atomic mass unit (amu). In the context of forming water (H₂O), hydrogen plays the role of a reducing agent while it combines with oxygen.

• Each hydrogen atom bonds with an oxygen atom to form water.
• In its gaseous state, hydrogen exists as a diatomic molecule, H₂.

The role of hydrogen in forming water illustrates fundamental principles of bonding and molecular structure, such as covalent bonding, where hydrogen shares its electrons with another element, like oxygen.

Oxygen

Oxygen is essential for life and forms part of the air we breathe. It has an atomic mass of around 16 amu, making it much heavier than hydrogen. Within the formation of water, oxygen acts as an oxidizing agent.

• It tends to attract electrons towards itself during bonding, illustrating its high electronegativity.
• In gaseous form, oxygen is usually found as a diatomic molecule, O₂.

Understanding oxygen's properties helps clarify why historically, it was considered much heavier than hydrogen, especially in the context of early interpretations of water's composition.

H₂O

Water, with its chemical formula of H₂O, consists of two hydrogen atoms and one oxygen atom. This formula indicates the molecular structure of water, where each molecule contains these three atoms in bonding arrangements.

• The two hydrogen atoms bond covalently with a single oxygen atom, forming a bent geometry.
• The actual mass ratio in water is reflective of this composition: \[ \text{(Hydrogen Mass: 2 amu) : (Oxygen Mass: 16 amu)} = 1:8. \]

This formula is fundamental in understanding not just water, but also principles of chemical reactions and molecular bonding, highlighting the balance of shared electrons between hydrogen and oxygen.