Which equation shows the synthesis of water? Place an \(\mathrm{X}\) on the blank next to your choice. $$ 2 \mathrm{Na}+\mathrm{Cl}_2 \rightarrow 2 \mathrm{NaCl} $$ $$ 2 \mathrm{H}_2+\mathrm{O}_2 \rightarrow 2 \mathrm{H}_2 \mathrm{O} $$ $$ \mathrm{NaOH} \rightarrow \mathrm{Na}+\mathrm{OH} $$ $$ 4 \mathrm{Fe}+3 \mathrm{O}_2 \rightarrow 2 \mathrm{Fe}_2 \mathrm{O}_3 $$

Chemical reactions are processes where substances, called reactants, are transformed into different substances, known as products. During these reactions, the chemical bonds between atoms are broken and reformed, leading to new substances with new properties. Chemical reactions can vary widely, from simple to complex. A good example is the formation of water from hydrogen and oxygen gas.

Here are some key points to remember about chemical reactions:

• Reactants are the starting materials, and products are the end results of the reaction.
• Chemical equations represent these reactions and show the relationship between reactants and products.
• Energy changes often occur, which can be in the form of heat, light, or electricity.

Balanced chemical equations are essential for accurately representing chemical reactions. In a balanced equation, the number of atoms of each element is the same on both sides of the reaction. This follows the Law of Conservation of Mass, which states that matter is neither created nor destroyed in a chemical reaction.

For example, the balanced equation for the synthesis of water is:



Key points about balanced chemical equations:

• The same number of each type of atom appears on both sides of the equation.
• Coefficients (the numbers in front of molecules) are used to balance the equation.
• Balancing ensures that the equation follows the Law of Conservation of Mass.
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In an unbalanced equation, the number of atoms for each element would not be the same on both sides, which misrepresents the actual reaction. Balancing involves adjusting coefficients to ensure equal numbers of each atom on both sides of the equation. For our specific example, the balanced equation for water synthesis confirms two parts hydrogen (H2) react with one part oxygen (O2) to create two parts water (H2O).

Synthesis reactions involve combining two or more simpler substances to form a more complex compound. In these reactions, multiple reactants join together to create a single product. The synthesis of water from hydrogen and oxygen is a classic example.

A general format for a synthesis reaction can be illustrated as:


The specific synthesis reaction for water is:

Key points about synthesis reactions:

• Involves two or more simpler substances forming one complex compound.
• Usually releases energy in the form of heat or light.
• Produces a single product from multiple reactants.

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By understanding such examples and practicing balancing them, students can master the fundamentals of synthesis reactions and their importance in chemistry. The synthesis of water, where hydrogen gas reacts with oxygen gas to form liquid water, is a crucial chemical reaction that highlights these principles.