Sunhonors Chemistry2nd Semester Review Problems

SunHonors Chemistry2nd Semester Review Problems

Review Problems for 2nd Semester

The following problems are continued from the Midterm Review problems. These problems are to help you to review some, but not all, of the concepts we learned during the 2nd semester. You may review Midterm review to get some practice for concepts we learned during the 1st semester. A detailed guideline for the final exam can be found in the document Final Exam Review Guide Honors11-12. The best way to study is to follow the instructions in that document and check your understandings for each objective listed there.

Internal Structure of the Atom and Compounds

1.How do interactions observed in the Sticky Tape experiment help us understand the attractions between ions, atoms and molecules in compounds?

2.Distinguish between molecular and ionic solids.
Particles in molecular solids are separate molecules that attract one another. When dissolved in water, the solution does NOT conduct electricity; e.g., C6H12O6. Give reasoning at particle level.

Particles in ionic solids are charged particles (ions). Cations (+) and anions (-) are in an alternating lattice pattern. The formula unit represents the simplest integer ratio (empirical formula) of the ions; e.g. CaCl2. When dissolved in water, the solution does conduct electricity. Give reasoning at particle level.

What other property differences between ionic and molecular compound can be explained by the particle model you describe above?

3. Demonstrate knowledge of the meaning of a chemical formula in terms of atoms and molecules.

Example: Identify the number of atoms and ions of each kind in each compound.
Pb(NO3)2Na3PO4Al2(SO4)3

4.Name ionic and molecular compounds from formulas and vice versa.
Write the formula or name of binary compounds (formed from two kinds of atoms).

a potassium iodide

b. nitrogen trichloride

sodium oxide

d. aluminum chloride

tin(IV) chloride

f. iron(III) sulfide

g.phosphorus tribromide

i.SnBr4

j.SO2

k.Al2O3

N2O5
CaO

Write the formula or name of compounds formed from polyatomic ions.

calcium nitrate
potassium phosphate
aluminum acetate
ammonium sulfate
Al(OH)3
Cu2SO4
(NH4)2CO3

The mole concept and chemical reactions

Recognize that atoms and molecules are too small to count directly. We use a counting unit – mole – to count them by bulk so we can determine how many atoms/molecules there are in a measurable sample by finding the mass. Therefore, mass of one mole of a substance (molar mass) can be used as a conversion factor between mass and mole. Mole was originally defined as the number of atoms in 1 gram of hydrogen. Molar mass of any substance can be found from the relative mass in the periodic table. Current definition of one is the number of atoms in 12 grams Carbon-12.

1.Be able to determine the molar mass of a compound.
Example: Determine the molar masses.Pb(NO3)2BaSO4

2.Determine the number of atoms or moles using Avogadro’s number and the molar mass of a compound.
Example:12 g MgCl2 x = molesMgCl2

3.0 moles MgCl2xx= ions Cl-

3. Determine the empirical and molecular formulas from mass data.

A compound is composed of 7.20 g of carbon, 1.20 g of hydrogen, and 9.60 g of oxygen. The molar mass of the compound is 1.8x102 g. Find the empirical and molecular formulas for this compound.

4.Distinguish between the meaning of coefficients and subscripts in a balanced chemical equation.
Example: Draw particle diagrams to represent the following reaction:

Al+ FeSO4 -->______+_____reaction type?

5.Write complete balanced reaction equations from word descriptions.
Change these word equations to symbols. Identify type of reactions.
a. barium chlorate, when heated, produces barium chloride and oxygen gas.
b. ethane, C2H6, burns in air to produce ______and ______.

c. lime, (calcium oxide) reacts with sulfur dioxide to form calcium sulfite.
d. chromium reacts with oxygen to produce chromium(III) oxide.

e. potassium carbonate powder reacts with hydrochloric acid to produce ______, carbon dioxide and water.

6.Demonstrate knowledge that matter is conserved in ordinary chemical reactions.
Example: If 3.6 g of water is decomposed, 3.2 g of oxygen and what mass of hydrogen will be produced?

Stoichiometry

1.Use balanced equation and the BCA table to predict the quantity of reactant or product involved in a chemical reaction.
Calculate the number of grams of potassium chloride, KCl, that will be formed by the decomposition of 6.45 g of potassium chlorate, KClO3.

2.Determine percent yield when actual yield is known.
A chemist burns 160 g of Al in air to produce 260 g of solid aluminum oxide. Determine the theoretical yield. Determine the percent yield.

3. From a representation of a reaction mixture before and after the reaction, determine the balanced equation for a reaction.

Reaction equation ______

4.Use limiting reactant to predict amount of product formed.
How many grams of water can be formed when 2.87 g of CH4 reacts with 4.58 g of O2? (Hint: predict reaction products first)

5.Apply law of partial gas pressure, molar volume at STP and/or ideal gas law (PV=nRT) to solve stoichiometry problems involving gases.

The above reaction between CH4 and oxygen was carried out in a container with constant volume of 5.00 L.After the reaction was completed, the resulting mixture was cooled to 62.6°C. What is the total pressure in the container?

a) What are the substances in the container at this point? What are in gas phase? (remember that water exists as liquid at 62.6°C but there is always water vapor in the gas phase above the surface of water)

b) How many moles of each gaseous substance are in the mixture? (no need to calculate moles of water vapor) Hint: Check the after line in your BCA table in question #4.

c) What is the partial pressure of each gas (not water) in the mixture? Hint: you already know the volume, mole and temperature of each gas.

d) What is the total pressure (in atm) in the container? (Water vapor pressure at 62.6°C is 171 mmHg.)

6. Determine the amount of energy absorbed or released by a chemical reaction from the given ∆H of reaction and stoichiometry.

a) The enthalpy change of the combustion of CH4 is ∆H = - 882.0 kJ/mol. Is this reaction endo- or exothermic? Write the reaction equation in two ways: 1) with the energy in kJ written on the correct side of equation; 2) in ∆H notation.

b) How many grams of water would be formed if 147 kJ of energy is released by the reaction?

c) If the amount of energy released by the reaction in question #4 is transferred to
1.00 kg of water, what would be the temperature change of water? Increase or decrease? Specific heat capacity of water is 4.18 J/(g°C).

7. Use molar concentration (molarity) of solution as a conversion factor in stoichimometry involving volume and mole of solutions.

a) How many mL of 3.04 M hydrochloric acid (HCl) is consumed in the reaction with 2.26 g of zinc? (predict reaction products and write a balanced reaction equation)

b) What is the volume of the gas product at STP? (You must use the most direct method.)

c) What is the volume of the gas product at 25°C and 752 mmHg? Try in two ways: the ideal gas law and PVnT table with proportional factors.

Modeling Chemistry11st Sem Review-v2.1