Compounds and Stoichiometry

Question 1

What are compounds?

Answer 1

pure substances composed of two or more elements in a fixed proportion

Question 2

What is a molecule?

Answer 2

combination of two or more atoms held together by covalent bonds

Question 3

What is a formula unit?

Answer 3

represents the empirical formula of the compound

Question 4

Molecular weight vs formula weight

Answer 4

Molecular weight - sum of atomic weights of the atoms

Formula weight - sum of atomic weights of the ions

Question 5

What is a mole?

Answer 5

a quantity of any substance and is defined by Avogadro’s number = 6.022 x 10^23. This based on the number of particles in 12 grams of carbon.

Question 6

What is the relationship between moles and molecular/formula weight?

Answer 6

one mole of a compound is equal to the molecular/formula weight of the compound

Question 7

What is molar mass?

Answer 7

the mass of one mole of a compound

Question 8

What is the equation for moles?

Answer 8

moles = mass of sample (g) / molar mass (g/mol)

Question 9

What is gram equivalent weight?

Answer 9

gram equivalent weight = molar mass / n

n = number of particles of interest produced or consumed per molecule of the compound in the reaction

Question 10

What is the equation for equivalents?

Answer 10

equivalents = mass of compounds (g) / gram equivalent weight (g)

Question 11

What is normality?

Answer 11

(N) measure of concentration - equivalents/L

Question 12

What is the equation for molarity?

Answer 12

Molarity = Normality / n

Question 13

What is the Law of Constant Composition?

Answer 13

any pure sample of a given compound will contain the same elements in an identical mass ratio

Question 14

What is the empirical formula?

Answer 14

the simplest whole number ration of elements in a compound

Question 15

What is the molecular formula?

Answer 15

exact number of atoms of each element in a compound

Question 16

What is percent composition formula?

Answer 16

% composition = mass of the element in formula/molar mass x 100

Question 17

What is a combination reaction?

Answer 17

has two or more reactants to form one product; always more reactants than products

Question 18

What is a decomposition reaction?

Answer 18

single reactant that breaks down into two or more products

Question 19

What is a combustion reaction?

Answer 19

special type of reaction that involves a fuel and oxidant; mostly reactants react to for carbon dioxide and water

Question 20

What is a single-displacement reaction?

Answer 20

occurs when an atom or ion in a compound is replaced by an atom or ion of another element

Question 21

What is a double-displacement reactions/metathesis reaction?

Answer 21

elements from two different compounds swap places with each other to form two new compounds

Question 22

What are neutralization reactions?

Answer 22

a specific kind of double displacement reactions in which an acid reacts with a base to produce a salt and usually water

Question 23

What are three rules of doing stoichiometry problems?

Answer 23

(1) Convert from given units to moles
(2) Use the mole ratio
(3) Convert from moles to the desired units

Question 24

What is theoretical yield?

Answer 24

the maximum amount of product that can be generated as predicted from the balanced equation, assuming that all the limiting reactant is consumed, no side reactions have occurred and the entire product has been collected

Question 25

What is the equation for percent yield?

Answer 25

percent yield = actual yield/theoretical yield x 100