Chemistry Exam 2

Titrations

100

Define a neutralization reaction

A reaction that takes place
when a strong acid reacts with a strong
base and produces a solution of a salt in
water

200

What are titration reactions used for?

It is a method for determining an unknown concentration by titrating it with something of a known concentration

300

Write a balanced reaction equation between sulufuric acid (H₂SO₄) and sodium hydroxide (NaOH).

H₂SO₄ (aq) + 2NaOH (aq) -> 2H₂O (l)+ Na₂SO_{4 (aq)}

400

If 30.34 mL of a 0.135 M solution of
hydrochloric acid (HCl) were required to
neutralize 25.00 mL of a sodium hydroxide
(NaOH) solution, what is the molarity of the
sodium hydroxide solution?

0.164 M NaOH

500

A 25.0 mL sample of 0.100 M nitric acid (HNO₃) is titrated with a 0.150 M potassium hydroxide (KOH) solution. Calculate the volume of KOH solution needed to reach the equivalence point

0.0167 L KOH

Redox

100

Define oxidation and reduction

Oxidation: Loss of electrons

Reduction: Gain of electrons

200

Recite the gist of the oxidation rules

Each atom in a pure element has O.N. = 0

In monatomic ion, oxidation number is the charge on the ion.

O.N. of atoms in a neutral molecule sum to zero;

O.N. of atoms in an ion sum to charge on the ion.

Oxygen = -2 in most compounds (except in peroxides where oxygen = -1)

Hydrogen = +1 (unless bound to a metal where H = -1)

Compounds that don’t contain O or H, refer to group number

• Fluorine, O.N. = -1 in all compounds.

• Br and Cl have -1 O.N., unless combined with O or F.

300

Assign oxidation numbers to each element

SO₂

CrO₄^2-

NH₃

S: +4, O: -2

Cr: +6, O:-2

N:-3, H:+1

400

Assign ON

ClO₃^-

SF₆

Cl₂

Cl: +5, O: -2

S: +6, F: -6

Cl: 0

500

Identify oxidized and reduced

CH₄(g) + 2 O₂(g) → CO₂(g) + 2 H₂O(g)

O: CH₄

R: O₂

Lewis/Orbitals

100

Calculate the valence electrons of NH₃

8 ve's

200

What is the electron configuration of Fe³⁺

1s²2s²2p⁶3s²3p⁶3d⁵

300

Calculate the valence electrons of SF₆ and draw the lewis structure. What is the electron pair geometry and the molecular geometry?

VE: 48

Structure on board, it is octahedral

Reactions

100

What does a precipitation reaction form

A solid product

200

Name a group of insoluble compounds

All hydroxides (OH–) except:

◦ Group IA (e.g, NaOH); Ca(OH)², Sr(OH)², and Ba(OH)²

 All sulfides (S₂^–) except:

◦ Group IA and NH₄⁺; CaS, SrS, and BaS

 All carbonates (CO₃^2–) except IA, NH₄⁺

 All phosphates (PO₄^3–) except IA, NH₄⁺

300

What do you combine to form the precipitate?

Pb(NO₃)₂(aq) + NaI(aq)

PbI₂ (s)

You combine the insoluble cation and insoluble anion

400

Form the net ionic reaction of: 

AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(s)

Ag⁺ (aq)+ Cl^- (aq) → AgCl(s)

Periodic Trends/ Wave functions

200

List a strength and weakness of the Bohr Model

Strengths:
◦ Accurately predicts energy needed to remove an
electron from an atom (ionization)
◦ Allowed scientists to begin using quantum theory
to explain matter at atomic level
Limitations:
◦ Does not account for spectra of multi-electron
atoms
◦ Didn’t predict atomic orbitals other than
spherical
◦ Assumed the electrons are only like particles

300

Calculate the energy of a photon of red light at 685 nm.

E= hc/λ

ℎ = Plank’s constant, 6.63 x 10^-34 J•s

c= 2.998 x 10⁸ m/s

2.90*10^-19 J