Chemistry Quiz Study Guide

The number of known elements at this time is approximately:

116 (We now know of approximately 116 different elements.)

Which one of the following is not part of Dalton's atomic theory?

Atoms change into other atoms in chemical reactions (Dalton's theory had four main concepts: (1) All matter is made of atoms. (2) Atoms of a given element are identical; atoms of different elements have different properties. (3) Chemical reactions involve the combination, not destruction, of atoms. (4) When elements react to form compounds, they react in defined, whole-number ratios.)

Although all parts of Dalton's atomic theory are important, which one of the postulates is crucial to explain the observations summarized by the Law of Definite Proportions?

Atoms chemically combine with other atoms in fixed, whole-number ratios (Chemical reactions are not random; rather, they proceed according to precise formulas. The Law of Definite Proportions states that atoms always react in defined proportions. For example, water is always made up of two parts hydrogen and one part oxygen.)

Which one of the following symbols represents a compound?

CO2 (Compounds are the chemical combination of two or more atoms of the elements. They are written as the symbols of the elements in them without any spaces. If more than one atom of an element is part of the compound, a subscript number shows how many atoms of that element are in one molecule of the compound.)

No matter how much extra oxygen is available, 12 grams of carbon always combines with 32 grams of oxygen. This best illustrates the law of:

Definite Proportions (Chemical reactions proceed according to precise formulas. For example, water is always made up of two parts hydrogen and one part oxygen. The Law of Definite Proportions states that atoms always react in defined proportions.)

Who proposed the first atomic view of matter?

Democritus (Democritus reasoned that matter is made from building blocks of infinitesimally small pieces which he called atomos, meaning "indivisible." He theorized that these were specific to the material that they made up and that different materials would be made up of different kinds of atomos.)

Which one of the following symbols represents an element?

He (Each of the elements has a one- or two-letter symbol. In this abbreviation for an element, the first letter is always capitalized and the second letter (if there is one) is always lowercase.)

Who first proposed the Law of Definite Proportions?

Proust (Proust established the Law of Definite Proportions, which states that atoms always react in defined whole-number ratios.)

Which one of the following statements concerning the relationship between the number of elements and the number of compounds is correct?

The number of compounds is much larger than the number of elements (The approximately 116 elements we know of form the basis of all of the materials around us. These building blocks can be combined chemically to form different compounds. Most of the substances we come into contact with are compounds rather than pure elements.)

Substances A and B combine chemically to form C. Substance C must be:

a compound (The chemical combination of two or more atoms of the elements results in a compound.)

A substance that cannot be broken down by chemical means into simpler substances is called a(n):

element (Elements are fundamental substances that cannot be broken down further by chemical means. They are pure substances that form the basis of all of the materials around us, the building blocks of the universe.)

The ancient Greeks believed that matter was composed of four basic materials. Which one of the following was not one of the four?

gold (The ancient Greeks believed that all matter was composed of four elements: fire, air, water, and earth. The ratio of these elements determined the properties of the matter, so, according to them, rabbits were living and soft because they had more water and fire.)

Joseph Priestley discovered:

oxygen (Priestley observed that when heated, a red stone called mercury calx breaks down into liquid mercury and a strange gas. The gas made flames burn brighter. Also, a mouse placed in a sealed container with this gas lived longer than a mouse placed in a sealed container of ordinary air. Priestley called the gas "dephlogisticated air," but the name was later changed to "oxygen.")

12 grams of carbon react with 32 grams of oxygen to form exactly 44 grams of carbon dioxide. This is a good example of:

the Law of Conservation of Mass (The Law of Conservation of Mass states that mass is not lost or gained during a chemical reaction.)