CHEM 101 - Exam 2

Percent Comp/Empirical Formula/Molecular Formula

100

Find the percent compositions of the elements in the following compound:

N₂S₂

N: 30.4% 

S: 69.6%

200

Find the percent compositions of the elements in the following compound:

CuBr₂

Cu: 28.4%

Br: 71.6%

300

What is the empirical formula for the compound which contains 32.8% Chromium and 67.2% Chlorine. Name this compound.

CrCl₃

Chromium (III) Chloride

400

What is the empirical formula for a compound that contains 80.2% zinc, and the rest is oxygen. Name the compound.

ZnO

Zinc Oxide

500

A compound with an empirical formula of C₂OH₄ and a molar mass of 132 grams per mole. Determine the molecular formula.

What is C₆O₃H₁₂?

Molarity & Dilutions

100

What is the FULL molality formula?

(moles of solute) ÷ (liters of solution)

200

If you dissolve 20.0 g of NaOH in 250.0 mL of water, what is the molarity of the solution?

What is 2.00 M?

300

If 45 mL of water are added to 250 mL of a 0.75 M K₂SO₄ solution, what will the molarity of the diluted solution be?

What is 0.64 M?

400

How much water in liters would need to be added to 750 mL of a 2.8 M HCl solution to make a 1.0 M solution?

What is 2.1 L?

500

 If the molarity of a solution is 0.500 mol/L, and it is made from 250.0 mL of water, how many moles of solute were added to the solution? 

What is 0.125 mol solute?

Precipitation Rxn

100

Precipitation Reactions usually undergo _________ __________ (a cation from one reactant combines with an anion of another reactant). 

What is double replacement?

200

Which of the following does not belong?

KOH

KBr

PbCO₃

K₂SO₄

What is PbCO₃? (insoluble)

300

Articulate the net ionic equation.

2KF(aq) + Mg(NO₃)₂(aq) → 2KNO₃(aq) + MgF₂(s)

Net ionic equation:

2F^-(aq) + Mg²⁺(aq) → MgF₂(s)

400

Determine the molecular equation AND the net ionic equation for the following precipitation reaction:

Potassium chromate and calcium chloride

Molecular equation:

K₂(CrO₄)(aq) + CaCl₂(aq) → 2KCl(aq) + Ca(CrO₄)(aq) 

Net ionic equation:

None-- all are spectator ions!

500

How many grams of silver chromate will precipitate when 150. mL of 0.500 M silver nitrate are added to 100. mL of 0.400 M potassium chromate?

What is 12.4 g Ag₂CrO₄?

Acid-Base Rxn

100

Which of the following does not belong?

HClO₄

H₃PO₄

HNO₃

HBr

What is H₃PO₄? (weak acid)

200

What is the pH range for each of the following?

Acids

Bases

Neutral compounds 

Acids: pH < 7

Bases: pH > 7

Neutral compounds: pH=7

300

What is the pOH of a 0.0235 M HCl solution?

What is 12.371?

400

Write out the molecular AND net ionic equation for the following:

Magnesium hydroxide and hydrochloric acid

Molecular equation: 

Mg(OH)2(aq) + 2HCl(aq) → MgCl2(aq) + 2H2O(l) 

Net ionic equation:

OH^-(aq) + H⁺(aq) → H2O(l)

500

What volume of 0.496 M HCl is required to neutralize 20.0 mL of 0.809 M sodium hydroxide? 

What is 0.0326 L HCl or 32.6 mL HCl?

Redox Rxn

100

True or False?

Oxidation is gain of electrons, reduction is loss of electrons.

What is false?

200

Determine the oxidation numbers for the elements in the following compound:

Na₂Cr₂O₇

Na: +1

Cr: +6

O: -2

300

Is the following a Redox reaction? 

C + H₂SO₄ → CO₂ + SO₂ + H₂O 

If yes, determine what is oxidized, what is reduced, the oxidizing agent, and the reducing agent.

Yes, this is a Redox reaction.

Carbon: oxidized, reducing agent

Sulfur: reduced, oxidizing agent

400

Write the reduction half reaction:

Fe²⁺ + MnO₄^- → Fe³⁺ + Mn²⁺

Reduction: Mn⁷⁺ → Mn²⁺

500

Using your activity series (given), determine whether the following reactions will or will not occur;

(1) Copper + sodium chloride solution →

(2) Zn + Ag⁺ →

(1) No reaction

(2) Zn²⁺ + Ag