Unit 1 - Introductory Concepts

Question 0

reactant

Answer 0

a starting substance in a chemical reaction; it appears to the left of the arrow in a chemical equation

Question 1

accuracy

Answer 1

a measure of how closely individual measurements agree with the correct value

Question 2

product

Answer 2

a substance produced in a chemical reaction; it appears to the right of the arrow in a chemical equation

Question 3

coefficient

Answer 3

the number that appears at the beginning of a term in a chemical equation

Question 4

hydrocarbons

Answer 4

compounds composed of only carbon and hydrogen

Question 5

diatomic molecule

Answer 5

a molecule composed of only two atoms

Question 6

synthesis (combination)

Answer 6

a chemical change in which atoms or molecules of two or more substances combine to form molecules of a single new substance

     2 H2 + O2 ---> 2 H2O

Question 7

decomposition reaction

Answer 7

a chemical reaction in which a single compound reacts to give two or more products

Question 8

combustion (hydrocarbon vs. metal)

Answer 8

a chemical reaction that proceeds with evolution of heat and usually also a flame; most combustion involves reaction with oxygen, as in the burning of a match

Question 9

single replacement (displacement) reaction

Answer 9

a reaction where one element is being displaced from a compound by another element

Question 10

double replacement (displacement) reaction

Answer 10

a chemical reaction where two reactant ionic compounds exchange ions to form two new product compounds with the same ions

Question 11

acid-carbonate reaction

Answer 11

a reaction between an acid and a carbonate forming a sale, carbon dioxide, and water as the only products

Question 12

law of conservation of mass

Answer 12

for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as system mass cannot change quantity if it is not added or removed

Question 13

law of constant composition (definite proportions)

Answer 13

a chemical compound always contains exactly the same proportion of elements by mass

Question 14

law of multiple proportions

Answer 14

if two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers

Question 15

John Dalton’s modern atomic theory

Answer 15

1) All matter is made of atoms.
2) All atoms of a given element are identical in mass and properties.
3) Compounds are formed by a combination of two or more different kinds of atoms.
4) A chemical reaction is a rearrangement of atoms.

Question 16

atomic number (Z)

Answer 16

the number of protons in the nucleus of an atom of an element

Question 17

mass number (A)

Answer 17

the sum of the number of protons and neutrons in the nucleus of a particular atom

Question 18

nuclear symbols

Answer 18

the symbol of the element, the atomic number of the element and the mass number of the specific isotope

Question 19

isotopes

Answer 19

atoms of the same element containing different numbers of neutrons and therefore having different masses

Question 20

natural abundancy

Answer 20

refers to the abundance of isotopes or a chemical element as naturally found on a planet

Question 21

atomic mass

Answer 21

the mass of an atomic particle, sub-atomic particle, or molecule

Question 22

electrons

Answer 22

a negatively charged subatomic particle found outside the atomic nucleus

Question 23

protons

Answer 23

a positively charged subatomic particle found in the nucleus of an atom

Question 24

neutrons

Answer 24

an electrically neutral particle found in the nucleus of an atom

Question 25

atomic mass unit

Answer 25

a unit based on the value of exactly 12 amu for the mass of the isotope of carbon that has six protons and six neutrons in the nucleus

Question 26

Avogadro’s number

Answer 26

the number it 12C atoms in exactly 12 g of 12C; it equals 6.0222 X 10^23 moles

Question 27

molar mass

Answer 27

the mass of one mole of a substance in grams; it is numerically equal to the formula weight in atomic mass units

Question 28

empirical formula

Answer 28

a chemical formula that shows the kinds of atoms and their relative numbers in a substance in the smallest possible whole-number ratios

Question 29

molecular formula

Answer 29

a chemical formula that indicates the actual number if atoms of each element in one molecule of a substance

Question 30

gaseous volume at STP

Answer 30

22.4 liters

one mole of an ideal gas will occupy a volume of 22.4 liters at STP

Question 31

STP

Answer 31

standard temperature and pressure

defined at 0°C and 1 atm pressure; frequently used as reference conditions for a gas

Question 32

molarity

Answer 32

the concentration of a solution expressed as moles of solute per liter of solution

Question 33

stoichiometry

Answer 33

the relationships among the quantities of reactants and products involved in chemical reactions

Question 34

mole ratio

Answer 34

ratio between the amounts in moles of any two compounds involved in a chemical reaction

Question 35

limiting reactant

Answer 35

the reactant in a chemical reaction that limits the amount of product that can be formed; the reaction will stop when all of the limiting reactant is consumed

Question 36

excess reactant

Answer 36

the reactant in a chemical reaction that remains when a reaction stops when the limiting reactant is completely consumed

Question 37

percent error

Answer 37

a percentage that expresses the difference between an approximate or measured value (experimental) and an exact or known value (theoretical)

Question 38

percent yield

Answer 38

the amount of product produced by a chemical reaction

the ratio of the actual (experimental) yield of a product to its theoretical (calculated) yield multiplied by 100

Question 39

gravimetric analysis

Answer 39

a technique through which the amount of an analyte (the ion being analyzed) can be determined through the measurement of mass

Question 40

percent composition

Answer 40

the percent of the total mass of the compound that is is due to that component