Princeton Ch 3 - Chemistry Fundamentals

Question 1

1mL = 1 ___?

Answer 1

1 mL = 1 cm3 = 1 cc –> 1 cubic centimeter

Question 2

What does Angstrom equal to?

Answer 2

10^-10 m. The Angstrom is convenient because atomic radii and bond lengths are typically around 1-3 A.

Question 3

Define density.

Answer 3

Mass per volume of a substance. Typically written as g/cm3.

Question 4

How does one convert g/cm3 –> kg/m3?

Answer 4

Multiply by 1000. For example, the density of water is

1 g/cm, which could be written as 1000 kg/m3.

Question 5

How do you convert kg/m3 –> g/cm3?

Answer 5

Divide by 1000.

Question 6

Define molecular formula.

Answer 6

A compound molecular formula gives the identities and numbers of the atoms in the molecule. H2O is a molecular formula.

Question 7

Define empirical formula.

Answer 7

The smallest whole numbers that give the same ratio of atoms. C6H12O6 –> CH2O

Question 8

See phone for polyatomic ions (or molecular ions) that you should be familiar with.

Answer 8

See phone. Polyatomic ions is a charged chemical species (ion) composed of two or more atoms covalently bonded or of a metal complex that can be considered to be acting as a single unit.

Question 9

Formula weight = atomic mass unit. What is an atomic mass unit?

Answer 9

One atomic mass unit is equal to exactly 1/12 the mass of an atom of carbon 12. The periodic table lists the atomic mass of each element, which is actually a weighted average of the atomic masses of all its naturally occuring forms (isotopes).

Question 10

How do we find the number of moles in a sample that contains 70% Fe and 30% Oxygen? How do we find the empirical formula from this?

Answer 10

Choose 100g. #moles Fe = 70g/(55.8g/mol) –> 5/4
#moles O = 30/(16g/mol) = 15/8;
Because the empirical formula involves the ratio of # of atoms, the ratio of Fe: O is (5/4)/(15/8) = (58)/(415) = 2/3
Fe2O3

Question 11

Define molarity.

Answer 11

Molarity (M) = #moles of solute/#liters of solution; [mol/L}

Question 12

Define mole fraction.

Answer 12

The fraction of moles of a given substance relative to the total moles in a solution.
mole fraction of S = Xs = (#moles of substance S)/ (total 3 of moles in solution)

Question 13

A chemical equation is _____ if, for every element represented, the # of atoms on the left side is equal to the # of atoms on the right side.

Answer 13

Balanced. This illustrates the Law of Conservation of Mass/Matter, which says the amount of matter (and thus mass) does not change in a chemical reaction.

Question 14

In the balanced equation 2Al + 6HCL –> 2AlCl3 + 3H2; how many moles of reach with one another?

Answer 14

This equation means that 2 moles of Al react with 6 moles of HCl to form 2 moles of AlCl3 and 3 moles of H2.

Question 15

See phone for balancing equations methods

Answer 15

Do it, fool.

Question 16

Describe what limiting reagent is.

Answer 16

The reactant we run out of first.

Question 17

Describe what an oxidation state is.

Answer 17

An atom’s oxidation state is mean to indicate how the atom’s ownership of its valence e- changes when it forms a compound. When Na forms NaCl with Cl, the Na atom will transfer its valence e- to the Cl atom. So the Na’s ownership has changed. We use +1 in this case. +1 = one less e-

Question 18

The oxidation state of any element in its standard state is____.

Answer 18

0.

Question 19

The sum of the oxidation states of the atoms in a neutral molecule must always be ___.

Answer 19

0.

Question 20

The sum of the oxidation states of the atoms in in a ion must always equal to _____.

Answer 20

The ion’s charge.

Question 21

Group 1 metals have a ____ oxidation state. Group 2 metals have a ____ oxidation state .

Answer 21

Group 1 metals have +1 oxidation state. Group 2 metals have +2 oxidation state.

Question 22

Hydrogen has a ____ oxidation state when bonded to something more EN than C and ____ when bonded on an atom less EN than C, and ____ when bonded to carbon.

Answer 22

+1, -1, 0.

Question 23

Oxygen has a _____ oxidation state.

Answer 23

-2. The rest of the atoms in the oxygen family also have a -2 oxidation state.

Question 24

Halogens have a ____ oxidation state.

Answer 24

-1

Question 25

Comment on the oxidation states of transition metals.

Answer 25

Like many other elements, transition metals can assume different oxidation states, depending on the compound they’re in.

Question 26

There are rules to assigning oxidation states. Name 1-4. See phone.

Answer 26

1) OS of any element in standard state is 0.
2) The sum of OS of the atoms in a neutral atom must always be 0; for ions, the sum must equal the charge. 3) Group 1 metals = +1 and group 2 metals = +2.
4) Fluorine has a -1 oxidation state.

Question 27

There are rules to assigning oxidation states. Name 5-7.

Answer 27

5) H has +1 when bonded to something more EN than C. H has -1 when bonded to something less EN than C. H has a 0 when bonded to C.
6) Oxygen has a -2 oxidation state.
7) The rest of the halogens have -1; the atoms of the oxygen family have a -2 oxidation state.