Question

State two experimental laws Dalton used to support the atomic theory.

Short answer

The two laws are the Law of Conservation of Mass and the Law of Definite Proportions.

Step-by-step solution

Understanding Dalton's Atomic Theory

Dalton's atomic theory proposed that matter is composed of indivisible particles called atoms. He used this concept to explain chemical reactions and laid the foundation for modern chemistry.

Law of Conservation of Mass

The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction. Dalton used this law to support his atomic theory by suggesting that atoms are rearranged during chemical reactions, but their total mass remains constant.

Law of Definite Proportions

The Law of Definite Proportions states that a chemical compound always contains its component elements in a fixed ratio by mass. Dalton supported his atomic theory by proposing that compounds are composed of specific combinations of atoms, leading to constant composition by mass.

Key concepts

Law of Conservation of Mass

The Law of Conservation of Mass is a fundamental concept in chemistry. It tells us that mass cannot simply vanish or appear out of nowhere during a chemical reaction. The atoms in the reactants are rearranged to form products, but the total mass stays the same. This principle was revolutionary when it came out. It showed that matter is conserved, even as substances change. This idea was crucial for Dalton. He used it to argue that atoms are solid, indivisible units that simply change partners during chemical reactions.
It's important to note a few key aspects:

• In any given chemical reaction, the mass of the reactants equals the mass of the products.
• Mass conservation holds true because atoms themselves are not destroyed or created.
• This law applies not just in small-scale lab reactions but also to natural processes happening in our world, from combustion to digestion.

Consider the example of water formation: - When hydrogen gas reacts with oxygen gas, water is produced. The weights of "H_2" and "O_2" consumed are the same as the "H_2O" produced. This consistent balance confirms the conservation of mass principle.

Law of Definite Proportions

The Law of Definite Proportions indicates that a chemical compound always contains the exact same proportion of elements by mass. This predictability is at the heart of what makes chemistry a science. No matter where or how a compound is synthesized, its composition by mass remains consistent.
Take common salt, or sodium chloride (NaCl), for example. It always consists of about 39.3% sodium and 60.7% chlorine by mass. Dalton saw this consistency as proof that compounds are made of specific, measurable numbers of atoms.
Key points about this law include:

• It underscores the idea that compounds have a fixed, predictable composition.
• The mass ratio of the elements in a compound does not depend on the method of preparation or the source of the compound.
• This idea supports the theory that chemical compounds are made up of specific types and numbers of atoms.

The Law of Definite Proportions is instrumental in understanding the purity of substances and in identifying compounds through quantitative analysis. It strengthened the atomic theory by suggesting that atoms indeed combine in consistent ways.

Chemical Reactions

Chemical reactions are processes where reactants are transformed into products. A chemical reaction involves breaking bonds in the reactants and forming new ones in the products. These changes are fundamental to chemistry and to understanding how substances interact.
Each reaction can be broadly described in terms of:

• Reactants, which are the starting substances.
• Products, which are the substances formed by the reaction.
• Conservation of Mass, where the mass of products equals the mass of reactants, demonstrating the rearrangement of atoms.

Chemical reactions come in various types, such as synthesis, decomposition, single replacement, and double replacement reactions. For instance, when hydrogen and oxygen gases react to form water, a synthesis reaction occurs. Here, two simple molecules combine to form a more complex product.
In every reaction, adherence to the Law of Conservation of Mass and the Law of Definite Proportions ensure the reaction's products are predictable and consistent. Chemical reactions are the core of chemical studies, forging foundational ties between theoretical concepts such as Dalton's Atomic Theory, and practical laboratory experimentation.