Unit 4 Key Terms and Concepts

Question 1

Formula Unit

Answer 1

an atom, a molecule, an ion, or a
combination of cations and anions that gives a
balance of charges. Anything represented by a
chemical formula.

Question 2

a Chemical Equation

Answer 2

uses chemical symbols to

represent what happens in a chemical reaction.

Question 3

(s)

Answer 3

Solid State

Question 4

(aq)

Answer 4

aqueous (dissolved in water) state

Question 5

(l)

Answer 5

liquid state

Question 6

(g)

Answer 6

gas state

Question 7

coefficients

Answer 7

indicate how many of the chemical units participate in the reactions

Question 8

balanced chemical equation

Answer 8

has the same number of atoms of each kind on both sides of the reaction

Question 9

Law of Conservation of Matter

Answer 9

matter is not
created or destroyed in chemical reactions. Mass
of products = mass of reactants.

Question 10

decomposition reaction

Answer 10

one substance splits into two or more simpler substances

Question 11

Combustion reaction

Answer 11

a reaction of a substance

with O2 that produce heat and light and oxide products. (CO2 and H2O)

Question 12

1 amu=

Answer 12

1.6605387 x 10−24 g

Question 13

proton mass

Answer 13

1.007 amu

Question 14

neutron mass

Answer 14

1.008 amu

Question 15

Average atomic mass (atomic weight)

Answer 15

the weighted average mass of naturally occurring

isotopes in a sample expressed in amu’s.

Question 16

Formula mass (formula weight)

Answer 16

the sum of the average atomic masses (atomic weights) of all the atoms in a formula unit. The mass of a compound in amu’s

Question 17

Percentage composition

Answer 17

is the percentage of each element in a compound by mass.

Question 18

percent composition equation

Answer 18

% element A = mass from element A/(total compound mass) x 100

Question 19

1 mol=

Answer 19

6.022 x 1023 formula units

Question 20

mole (mol)

Answer 20

an amount of substance containing
the same number of formula units as there are
atoms in 12.000 g of ^12C.

Question 21

molar mass

Answer 21

the mass in grams of one mole of a

substance. Numerically equal to formula weight.

Question 22

The formula mass of water

Answer 22

2(1.008) + 16.00 = 18.02 amu

Question 23

The molar mass of water

Answer 23

2(1.008) + 16.00 = 18.02 g/mol

Question 24

The mole is the SI unit for

Answer 24

an amount of substance

Question 25

Molecular Formula

Answer 25

The actual numbers of atoms or moles of each element in a compound

Question 26

empirical formula

Answer 26

a chemical formula that gives the smalles whole number ratios of atoms or moles of each element in a compound

Question 27

How do you find the empirical formula from a moleuclar formula?

Answer 27

Reduce the subscripts as much as possible. | ex: C6H12O6= CH2O

Question 28

C6H6 Empirical Formula

Answer 28

CH

Question 29

Na2SO4 Empirical Formula

Answer 29

NaSO2

Question 30

C6H14 Empirical Formula

Answer 30

C3H7

Question 31

C5H12

Answer 31

C5H12

Question 32

How do you find the molecular formula from an empirical formula?

Answer 32

Step 1: You must know the formula weight or molar mass of the compound Step 2: Compare the mass of the molecule to the mass of the empirical formula unit. Express this as a whole number Step 3: Multiply the subscripts by the whole number factor

Question 33

Percentage Composition can help identify compounds by

Answer 33

comparing experimental percentages to percentages in known compounds

Question 34

Stoichiometry

Answer 34

the relationships among the amounts of reactants and products in a chemical reaction in terms of moles (Mole Bookkeeping)

Question 35

When Determining how many moles of an element are in a specific weight of the same element, what are the procedures?

Answer 35

Use dimensional analysis to multiply the given amount times (1 mol of the element divided by the weight of the element) Ex. How many Moles of Zn are in 116 g of Zn. 116 g Zn*(1mol Zn/65.39 g Zn)... The g Zn will cancel out each other and leave the answer in grams.

Question 36

When Determining how many moles of a compound are in a specific weight (in Grams) of the same compund, what are the procedures?

Answer 36

Use Dimensional Analysis to multiply the given amount times (1 Mol of the compound/mass of the compound) Ex: How many Moles of Sodium Bicarbonate are in 25.0 g Sodium Bicarbonate? 25.0 g NaHCO3x(1 mol NaHCO3/84.008 g NaHCO3)

Question 37

When determining how many moles of an atom are in a specific amount (In grams) of a compound, what are the procedures?

Answer 37

Use Dimensional Analysis to multiply the given amount times (1 mol of the compound/mass of the compound)x(the number of atoms of the element in the compound/1 mol of the compound) Ex: How many moles of oxygen atoms are in 245 g of Chromium (III) Sulfate) 245 g Cr2(SO4)3 * (1 Mol Cr2(SO4)3/392.21 g Cr2(SO4)3) *(12 mol O/1Mol Cr2(SO4)3).... This leaves our end result in moles of oxygen as requested.

Question 38

When determining how many moles of an element's atoms are in a specific amount (In moles of a compound, what are the procedures?

Answer 38

Use Dimensional Analysis to multiply the given amount times (the # of atoms in the compound formula/1 mol of the compound) Ex. Moles of Hydrogen atoms in 4.80 mol of calcium acetate 4.80 mol Ca(C2H3O2)2 * (6 Mol H/1 Mol Ca(C2H3O2)3)

Question 39

When determining how many atoms are in a specific amount (in moles) of an element, what are the procedures?

Answer 39

Use Dimensional Analysis to multiply the given amount times (Avogadro's Number/1 Mol of the element) Ex. How many atoms are in 7.65 mol of Cu? 7.65 mol Cu *(6.022*10^23/1 Mol Cu)

Question 40

When determining how many molecules are in a specific amount (in grams) of a compound, what are the procedures?

Answer 40

Use Dimensional Analysis to multiply the given amount times ( 1 mole of the compound/ mass of the compound) * (Avogadro's #/1 mol of the compound) Ex. How many molecules of C6H6 are in a 150 g sample of C6H6? 150.0 g C6H6 * (1Mol C6H6/78.108 g C6H6)* (6.022*10^23/1 mol C6H6)

Question 41

When determining the formula Units in a specific amount (in grams) of a compound, what are the procedures?

Answer 41

Use Dimensional Analysis to multiply the given amount times *(1 Mol of the compound/mass of the compound)*( Avogadro's #/ 1mol of the compound) Ex: How many formula Units of NaCLO4 are in 500.0 g od NaCLO4? 500.0 g NaClO4*(1 mol NaClO4/122.44 g NaClO4) *(6.022*10^23 formula Units NaClO4/1 mol NaClO4)

Question 42

When determining the mass(g) of a compound given in moles, what are the procedures?

Answer 42

Multiply the given amoutn times (mass of compound/1 mol of the compound). This will give the result in grams. Ex. What is the mass of 3.25 mol of Barium Chloride? 3.25 mol BaCl2 *(208.2 g BaCl2/1 mol BaCl2)