Problem 84 - Chemistry Matter and Change

Question

If you have 100 particles of hydrogen and 100 particles of oxygen, how many units of water can you form? Will you use all the particles of both elements? If not, what will remain?

Step-by-Step Solution

Answer

You can form 50 units of water, using all hydrogen particles and leaving 50 oxygen particles remaining.

Step 1: Determine the Chemical Formula for Water

The chemical formula for water is represented as \(H_2O\), meaning each water molecule is composed of two hydrogen (H) atoms and one oxygen (O) atom.

Step 2: Calculate the Maximum Number of Water Molecules

To form water, each molecule requires 2 hydrogen atoms and 1 oxygen atom. Given 100 hydrogen atoms, you can pair them into 50 pairs (since \( \frac{100}{2} = 50 \)). Meanwhile, you only need 1 oxygen atom for each water molecule, so from 100 oxygen atoms, you can make 100 water molecules. Therefore, you can create a maximum of 50 water molecules limited by the amount of hydrogen atoms.

Step 3: Determine Remaining Particles

After forming 50 water molecules, you will use up 100 hydrogen atoms (2 for each molecule). However, you will only need 50 oxygen atoms (1 for each water molecule). Thus, you will have 50 oxygen atoms remaining.

Key Concepts

Chemical Reactions

Chemical reactions involve the transformation of substances through the rearrangement of atoms. When substances come together, they may interact and convert into different molecules. In the context of forming water, a chemical reaction happens when hydrogen and oxygen combine.
A chemical formula represents these reactions succinctly. For water, the formula is \( H_2O \). This means each molecule of water requires 2 hydrogen atoms and 1 oxygen atom.
The process involves breaking old bonds and forming new ones, where energy may be absorbed or released.

• Reactants: The starting materials (in this case, hydrogen and oxygen).
• Products: The substances formed (water).

Understanding this core principle helps you predict the products and leftovers in any reaction.

Molecular Composition

Molecular composition determines how substances interact in a chemical reaction. Each element has distinct properties and reacts according to its atomic structure. For water, understanding the composition helps in predicting how many molecules can be formed.
Let's break this down:

• Hydrogen molecules consist of two hydrogen atoms. To form water, each of these provides a single hydrogen atom to pair with oxygen.
• Oxygen, being a single atom in water formation, can pair with two hydrogen atoms to create one water molecule.

Given 100 hydrogen atoms and 100 oxygen atoms, the molecular composition dictates that you can pair hydrogen atoms into 50 doublets to match with oxygen, resulting in 50 water molecules.

Limiting Reactants

In chemical reactions, a limiting reactant is the substance that is entirely consumed first, stopping the reaction from continuing. Identifying the limiting reactant can help in calculating the amount of product formed.
In this scenario:

• Each water molecule formation requires 2 hydrogen atoms and 1 oxygen atom. Therefore, hydrogen is utilized faster as you need more of it.
• With 100 hydrogen atoms available, you can only create 50 water molecules, because this amount will completely consume the hydrogen atoms.

Thus, hydrogen is the limiting reactant because once it is used up, no more water can be formed even if there are still oxygen atoms remaining. This concept is essential in predicting outcomes of reactions and reinforces the importance of exact quantities in chemical processes.