Chem 4 - Sample Exam #3
Sample Exams are designed to give you an idea of the types of questions you can expect. Exam numbers may not exactly agree with currently assigned material, so you may need to examine other sample exams to see questions that might be on the upcoming exam.
1. Indicate the total number of valence electrons present in each of the following compounds and then draw correct Lewis Dot structures for each:
NO
H2O
NH3
H2SO4
2. You start with 4 L of nitrogen gas at 0oC and 2.5 atm. What will be the volume of this gas if you raise the temperature to 100oC and change the pressure to 3.5 atm?
3. How much heat is required to raise the temperature of 22.5 g water from 15oC to 40oC? Express your answer in both calories and joules (J). (1 calorie = 4.184 J)
4. When you increase the molar mass of a compound, you increase its boiling point (B.P.). Polarity also affects B.P. Please show which compound in each pair would have the higher B.P.
CH4 or CCl4
CH4 or NH3
NH3 or PH3
Ar or Ne
H2O or H2S
HBr or HCl
5. You dissolve 7.50 g NaNO3 in 75.0 g H2O. Calculate the percentage concentration of NaNO3 in this solution. If you produced exactly 80.0 mL of volume, what would be its molarity?
6. You have 125.0 mL of acetic acid and neutralize it with 135 mL of 0.225 M NaOH. From these date, what is the concentration of acid in your 125.0-mL sample? How many moles of NaOH were used to perform this neutralization?
7. Based on the solubility rules predict which of the following substances are likely to be soluble in water (Check Yes, if soluble; No if insoluble).
___ Yes ___ No Barium nitrate
___ Yes ___ No Potassium carbonate
___ Yes ___ No Calcium sulfate
___ Yes ___ No Cu(OH)2
___ Yes ___ No Mercury(I) chloride
___ Yes ___ No Nickel(II) sulfide
___ Yes ___ No Sodium phosphate
___ Yes ___ No Silver(I) chloride
___ Yes ___ No Iron(II) nitrate
___ Yes ___ No Lead sulfate
8. Answer the following True/False questions:
___ T ___ F A strong acid is one that does not ionize very well
___ T ___ F Since NaCl is ionic, it always conducts electricity, whether solid or in solution
___ T ___ F All compounds containing the S2- ion are insoluble in water
___ T ___ F Every reaction that undergoes oxidation uses oxygen as the oxidizing agent
___ T ___ F When an atom gains electrons, it is reduced and becomes an anion
___ T ___ F When Zinc reacts with HCl, Cl2 and H2 gases are produced
___ T ___ F Combustion reactions always product water and carbon monoxide
___ T ___ F A decomposition reaction is the formation of water from H2 and O2
___ T ___ F The reaction between H+ and OH- is often called an acid-base reaction
___ T ___ F The ionic compound produced from an acid-base reaction is a salt
___ T ___ F The mass percentage of hydrogen in water is 100%
___ T ___ F For this reaction C + O2 --> CO2, 1 gram of C reacts with exactly 1 gram O2
___ T ___ F Spectator ions are not important
9. Show the products (if any), and then balance the following equations. Then, write the net ionic equations.
Ba(NO3)2+ H2SO4 -->
Na2CO3 + CoCl2 -->
KOH + HCl -->
10. What is Boyles's Law?
What is Charles' Law?
What is Avogadro's gas Law?
11. Using the universal gas equation (PV=nRT), determine the volume for 7.5 grams of H2 gas at 25oC and 1.5 atm pressure? What is the number of moles of hydrogen gas present? (Be sure to include all units to avoid mistakes. The universal gas constant is R=0.082 L.atm/mol.K.)
12. Convert the following into the units indicated:
0.903 atm = ________________________________ mm Hg (or torr)
25oF = ________________________________ Kelvin
1.25 L = _________________________________ mL
13. From the equation PV=nRT, you can get: P1V1 / T1 = P2V2 / T2 where P1, V1 and T1 are the initial pressure, volume and temperature of the gas. Using this equation, solve for P2 when:
P1 = 2.5 atm -- P2 = ???
V1= 2.7 L -- V2 = 4.3 L
T1 = 300 K -- T2 = 350 K
14. What volume does 3.5 moles of N2 occupy at STP (clue: what is the volume of 1 mole at STP?)?
EXTRA CREDIT (4 points):
You react 10 gram Zn with excess HCl. Show the reaction and correctly balanced equation. Then, how many moles and how many grams of H2 gas will you produce? Finally, how many Liters of H2 gas will you produce at STP?
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