Chemistry Chapter on Ancient Philosophy and Laws

Maharishi Kanad believed that matter could be divided into smaller pieces.

Pakudha Katyayama expanded on Maharishi Kanad's ideas by stating that these particles combine to form different kinds of matter.

Democritus and Leucippus believed that matter could be divided into smaller pieces.

<p>The ideas of Democritus and Leucippus were not scientifically tested until the 18th century.</p> Signup and view all the answers

<p>Antoine L. Lavoisier laid the foundation for modern chemistry.</p> Signup and view all the answers

<p>The Law of Conservation of Mass states that mass can neither be created nor destroyed in a chemical reaction.</p> Signup and view all the answers

<p>An example is the electrolysis of water, where water (H₂O) is split into hydrogen (H₂) and oxygen (O₂). The total mass of the water before the reaction is the same as the combined mass of the hydrogen and oxygen after the reaction.</p> Signup and view all the answers

<p>The Law of Constant Proportions states that a particular chemical compound always contains the same elements in the same proportion by mass, regardless of its source or method of preparation.</p> Signup and view all the answers

<p>A chemical compound always has the same elements in the same fixed proportion by mass.</p> Signup and view all the answers

<p>Water (H₂O) always contains hydrogen and oxygen in a mass ratio of 1:8. This ratio remains constant, regardless of the origin of the water.</p> Signup and view all the answers

<p>According to Dalton's Atomic Theory, all matter is made of very tiny particles called atoms.</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>True</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>Atoms combine in the ratio of small whole numbers to form compounds.</p> Signup and view all the answers

<p>The relative number and kinds of atoms are constant in a given compound.</p> Signup and view all the answers

<p>Atoms are the tiny, fundamental building blocks of all matter, essential to everything in the world despite their minuscule size.</p> Signup and view all the answers

<p>Atoms are comparable to bricks in a building or grains of sand in an ant-hill.</p> Signup and view all the answers

<p>True</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>Element symbols are derived from their names, using the first one or two letters, and standardized by IUPAC, ensuring each element has a unique symbol.</p> Signup and view all the answers

<p>Dalton was the first to use symbols for elements in a specific sense.</p> Signup and view all the answers

<p>Berzelius suggested that element symbols should be derived from one or two letters of the element's name.</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>An example is the element iron, whose symbol is Fe, derived from the Latin word ferrum.</p> Signup and view all the answers

<p>Atomic mass is the relative mass of an atom compared to 1/12th the mass of a Carbon-12 atom.</p> Signup and view all the answers

<p>Dalton's Atomic Theory introduced the concept of atomic mass, proposing that each element has a characteristic atomic mass.</p> Signup and view all the answers

<p>The concept of atomic mass helps explain the Law of Constant Proportions by providing a basis for understanding the relative proportions of elements in compounds.</p> Signup and view all the answers

<p>Individual atomic masses are difficult to measure directly, while relative atomic masses are determined using laws of chemical combinations.</p> Signup and view all the answers

<p>Carbon-12 was chosen as the standard reference due to its relatively common availability and the fact that its atomic mass is close to a whole number (12 units).</p> Signup and view all the answers

<p>Molecules of elements consist of identical atoms, ranging from single-atom molecules to complex structures with many atoms, with their atomicity indicating the number of atoms in each molecule.</p> Signup and view all the answers

<p>Molecules of elements can be classified as single-atom molecules, diatomic molecules, or triatomic molecules.</p> Signup and view all the answers

<p>An example of a single-atom molecule is helium (He).</p> Signup and view all the answers

<p>An example of a diatomic molecule is oxygen (O₂).</p> Signup and view all the answers

<p>Atomicity is the number of atoms in a molecule.</p> Signup and view all the answers

<p>Molecules of compounds are formed by atoms of different elements combining in definite mass ratios.</p> Signup and view all the answers

<p>The main elements in water are hydrogen and oxygen, with a combining ratio by mass of 1:8.</p> Signup and view all the answers

<p>The main elements in ammonia are nitrogen and hydrogen, with a combining ratio by mass of 14:3.</p> Signup and view all the answers

<p>The main elements in carbon dioxide are carbon and oxygen, with a combining ratio by mass of 3:8.</p> Signup and view all the answers

<p>Ions are charged particles that can be single atoms or groups of atoms, with negatively charged ions called anions and positively charged ions called cations.</p> Signup and view all the answers

<p>Ions are charged species in compounds of metals and nonmetals, and can be a single charged atom or a group of atoms with a net charge.</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>An example of a polyatomic ion is the sulfate ion (SO₄²⁻).</p> Signup and view all the answers

<p>The chemical formula of a compound represents its composition using element symbols and valencies, with rules for balancing charges, order of elements, and notation for polyatomic ions.</p> Signup and view all the answers

<p>A chemical formula is a symbolic representation of a compound's composition.</p> Signup and view all the answers

<p>Valency is the combining power or capacity of an element and is used to determine how atoms of different elements combine.</p> Signup and view all the answers

<p>Valency can be thought of as the &quot;arms&quot; of an atom. For example, an octopus with 8 arms and humans with 2 arms.</p> Signup and view all the answers

<p>Molecular mass is the sum of the atomic masses of all atoms in a molecule.</p> Signup and view all the answers

<p>Molecular mass is the sum of atomic masses of all atoms in a molecule.</p> Signup and view all the answers

<p>Expressing molecular mass in atomic mass units provides a relative measure of a molecule's mass compared to other molecules.</p> Signup and view all the answers

<p>Formula unit mass is the sum of atomic masses in a formula unit of an ionic compound.</p> Signup and view all the answers

<p>The calculation of formula unit mass is similar to molecular mass, involving the summation of atomic masses of the atoms present in the formula unit.</p> Signup and view all the answers

<p>Molecular mass applies to molecular compounds, while formula unit mass applies to ionic compounds.</p> Signup and view all the answers

<p>Molecular mass is used for substances whose constituent particles are molecules.</p> Signup and view all the answers

<p>Formula unit mass is used for substances whose constituent particles are ions.</p> Signup and view all the answers

<p>Molecular mass is used to calculate the mass of a single molecule of a substance.</p> Signup and view all the answers

<p>The formula unit mass of calcium chloride (CaCl₂) can be calculated by adding the atomic mass of calcium (Ca) which is 40 u, and twice the atomic mass of chlorine (Cl) which is 35.5 u. This gives a total formula unit mass of 111 u.</p> Signup and view all the answers

<p>The formula unit mass of sodium chloride (NaCl) can be calculated by adding the atomic mass of sodium (Na) which is 23 u, and the atomic mass of chlorine (Cl) which is 35.5 u. This gives a formula unit mass of 58.5 u.</p> Signup and view all the answers