SCH3U Test #3 (Ch. 5, 6, 7)

Question 1

Define anhydrous

Answer 1

A term used to describe a compound that does not have any water molecules bonded to it; applies to compounds that can be hydrated.

Question 2

What is a carbon-hydrogen combustion analyzer?

Answer 2

It is a device that uses the combustion enabling properties of oxygen gas to determin the composition of compounds containing hydrogen, carbon and another element like oxygen.

Question 3

Define empirical formula

Answer 3

Shows the lowest whole number ratio of atoms of each element in a compound.

Question 4

What is a hydrate?

Answer 4

This is a compound that has a specific number of water molecules bonded to each formula unit.

Question 5

What does the Law of Definite Proportions state?

Answer 5

It states that the elements in a chemical compound are always present in the same proportions by mass.

Question 6

Define mass percent

Answer 6

The mass of a solute divided by the mass of the solution, expressed as a percent.

Question 7

What is a molecular formula?

Answer 7

A formula that shows the actual number of atoms of each element in a molecule or formula unit.

Question 8

Define percentage composition

Answer 8

The relative mass of each element in a compound.

Question 9

Define Average atomic mass

Answer 9

The average of the masses of all the isotopes of an element; given in atomic mass units (u)

Question 10

Define Isotopic abundance

Answer 10

The relative amount of an isotope of an element; expressed as a percent or a decimal fraction.

Question 11

Define mole

Answer 11

The SI base unit for amount of substance; contains the same number of atoms, molecules, or formula units as exactly 12 g of carbon-12.

Question 12

Define weighted average

Answer 12

An average that takes into account the abundance or importance of each value.

Question 13

Define Avogadro constant

Answer 13

The experimentally-determined number of particles in 1 mol of a substance; the currently accepted value is 6.022 141 99x10^23

Question 14

Define mass spectrometer

Answer 14

An instrument that uses magnetic fields to separate the isotopes of an element and measure the mass and abundance of each isotope.

Question 15

Define molar mass

Answer 15

The mass of 1 mol of a substance, numerically equal to the element’s average atomic mass; expressed in g/mol.

Question 16

Actual yield

Answer 16

The measured quantity of product obtained in a chemical reaction.

Question 17

excess reactant

Answer 17

The reactant that remains after a reaction is over.

Question 18

mole ratios

Answer 18

Ratios that compare the number of moles of different substances in a balanced chemical equation.

Question 19

percentage yield

Answer 19

The actual yield of a reaction, expressed as a percent of the theoretical yield.

Question 20

coefficient

Answer 20

In a balanced chemical equation, a positive number that is placed in front of a formula to show how many units of the substance are involved.

Question 21

competing reactant

Answer 21

A reaction that occurs at the same time as a principal reaction and consumes the reactants and/or the products of the principal reaction

Question 22

limiting reactant

Answer 22

The reactant that is completely consumed during a chemical reaction, limiting the amount of product produced.

Question 23

percentage purity

Answer 23

The percent of a sample that is composed of a specific compound or element.

Question 24

stoichiometric amounts

Answer 24

The exact molar amounts of a reactant or a product, as predicted by a balanced chemical equation.

Question 25

stoichiometry

Answer 25

The study ofthe mass-mole-number relationships in chemical reactions and formulas.

Question 26

theoretical yield

Answer 26

The amount of product that is produced by a chemical reaction as predicted by the stoichiometry of the chemical equation.