Chm 110 Test 2 Chs 3,4,5 Name
CHM 110 TEST 2 CHS 3,4,5 NAME
Write your answers to the following questions. If a calculation is involved, use the correct number of significant figures in your answer. A periodic chart and table of conversions is given. Do not consult your text covers. All questions are 10 points each. 1-10 must be attempted before starting 11.
1. Classification of substances
a. Which of the following compounds are strong electrolytes?
HNO3, NaNO3
b. Which of the following compounds are weak electrolytes?
H2CO3, Pb(OH)2, Be(OH)2, NiSO4,
c. Which of the following compounds are strong acids?
HNO3
d. Which of the following compounds are weak bases?
Pb(OH)2, Be(OH)2
e. Which of the following compounds are nonelectrolytes?
C2H5I, N2O4
2. Complete, balance and classify the following reactions
a) Carbonic Acid aqueous à CO2 + H2O
b) C4H8O gas + Oxygen gas à 4CO2 + XH2O
FIND X
c) Chromium(II) Nitrate aqueous + sulfuric acid à CrSO4 + 2HNO3
d) Berrylium solid + Ferrous chloride aqueous à BeCl2 + Fe
e) Zinc solid + Oxygen gas à 2ZnO
3. Calculate average atomic mass of zinc. Zinc exists as four stable isotopes.
Zn - 064 48.6% 63.929146 amu
Zn - 066 27.9% 65.926036 amu
Zn - 067 4.1% 66.927130 amu
Zn - 068 18.8% 67.924847 amu
TYPE / % COMP / AMU64 / 48.6 / 63.929146 / 31.069565
66 / 27.9 / 65.926036 / 18.393364
67 / 4.10 / 66.927130 / 2.744012
68 / 18.8 / 67.924847 / 12.769871
Ave Atomic mass / 64.976812
4. Find the empirical formula for a compound that contains 92.258 % C and 7.742 % H. If the compound has a molar mass of 104 amu, what is its molecular formula?
Mass element g / Moles element / ratios / Empirical wt / N = mol wt/empwt92.258 / 7.681126 / 1 / 13.01894 / 7.98836
7.742 / 7.68101276 / 1
CH empircal formula / C8H8 molecular formula
5. Aluminum carbide and water react to form aluminum hydroxide and methane, CH4.
A) If 200g of aluminum carbide are reacted with 200g of water, how much methane will be formed? B) What is the limiting reagent? C) If 46 g of methane gas are actually formed by this reaction, what is the % yield of methane for the reaction?
Al4C3 (s) + 12 H2O (l) à 4 Al(0H)3 (s) + 3 CH4 (g)
Al4C3 (s) + / 12 H2O (l) / à / 4 Al(0H)3 (s) + / 3 CH4 (g)MW / 143.95916 / 18.01528 / 78.00356 / 16.04276
Gram / 200 / 200 / 44.5254
Mole Al4C3 / 1.38928 / 4.16784
Mole H20 / 11.10169 / 2.77542
Limiting reagent / % Yield = / 103.3118
% Yield = 46g/66.86g * 100 % =
6. A) Complete and balance the reaction which will occur? Use the data from Table 4.5.
Cr (s) + NiSO4(aq) à
Ni (s) + CrSO4(aq) à
See electrochemical series chart for answers here.
B) Which element is oxidized?
C) Which element is reduced?
D) What are the oxidation numbers of the oxidized and reduced elements before and after the reaction?
E) Does an element gain or lose electrons when it is reduced?
Element gains e-s when reduced
7. i) Label the following reactions as exothermic or endothermic.
a) 2Mg(s) + O2(g) -----à 2MgO(s) DHo = -1203.6 kJ
EXO
b) Mg(OH)2(s) à MgO(s) + H20(l) DHo = +37.1 kJ
ENDO
c) 2H2(g) + O2(g) à 2H2O(l) DHo = -571.7 kJ
EXO
ii) Using the data from the above reactions calculate DHo for the formation of solid magnesium hydroxide.
DHo kJMgO(s) + / H20(l) / à / Mg(OH)2(s) / -37.1
1H2(g) + / 1/2O2(g) / à / 1H2O(l) / -285.85
1Mg(s) + / ½ O2(g) / à / 1MgO(s) / -601.8
1Mg(s) +1H2(g) / + 1 O2(g) / à / Mg(OH)2(s) / -924.75
iii) Will heat be released or absorbed in the formation of solid magnesium hydroxide?
released
iv) Is the formation of solid magnesium metal exothermic or endothermic?
endothermic
v) How much heat will be absorbed or released to form 103 g of solid magnesium hydroxide?
DHo kJ/mol1Mg(s) +1H2(g) / + 1 O2(g) / à / Mg(OH)2(s) / -924.75
GRAMS / 103
MW g/mol / 58.31968 / DHo kJ
mole / 1.76613 / -1633.22872
8. A) Determine the energy required to raise the temperature of 250g of copper from 25oC to 100oC in Joules. (B) What is this value in calories if 1 cal = 4.184 J? (C) What would be the final temperature of 50 g t-butyl alcohol at 25oC if the t-butyl alcohol absorbed all of heat used to raise the temperature of copper from 25oC to 100oC. Use the data from Appendix 1. Need heat capacities…of Cu of t-butyl alcohol.
Use q = mCDT
9. A) How many grams of HClO4 are required to prepare 250 mL of a 0.500 M solution of HClO4?
grams of HClO4 = (0.500 mol/L)*(250 mL) * (1 L/1000 mL) * gMW HClO4
B) What is the final volume of 50 mL of 0.500 M solution of HClO4 diluted to a concentration of 0.115M HClO4?
V2 = V1*(M1/M2) = 50 mL * (0.500M/0.115M)
C) What volume of 0.115 M HClO4 is required to neutralize a 75g of NaOH?
Mole OH- = mole NaOH = 75g/gMW NaOH
For neutral solution mole OH- = mole H+
NA*VA = mole H+ = mole OH-
VA = (75g/gMW NaOH)/(0.115 N HClO4 ) in L
D) What is the concentration of an NaOH solution if 40 mL of 0.115 M HClO4 is required to neutralize 25 mL of the NaOH solution?
NB = NA*(VA/VB) = 0.115 N * (40 mL/25 mL)
NB = MB
E) How many grams of HClO4 are required to neutralize 35 mL of a O.400 M solution of NaOH?.
grams of HClO4 = g MW HClO4 * 0.400 N NaOH * 35 mL * 1 L/1000 mL
10. Sodium phosphate is reacted with Calcium nitrate in aqueous solution.
a) Write and balance the full equation for this reaction.
2 Na3PO4(aq) + 3 Ca(NO3)2 (aq) à Ca3(PO4)2(s) + 6 NaNO3(aq)
b) Write the total ionic equation for this reaction.
6Na1+ (aq) + 2PO4 3-(aq) + 3 Ca 2+ (aq) + 6NO3 1- (aq)
à Ca3(PO4)2(s) + 6 Na 1+(aq) + 6NO3 1-(aq)
c) Write the net ionic equation for this reaction.
2PO4 3-(aq) + 3 Ca 2+ (aq) à Ca3(PO4)2(s)
d) Which substance tends to easily decompose to carbon dioxide and water when formed and shaken?
H2CO3
e) Are precipitates strong or weak electrolytes?
WEAK
11. Suppose you have a soccer ball.
a) What kinds of energy may the ball possess.?
PE AND KE
b) What is the value of the kinds of energy when the ball is still on the ground with no place to roll or fall?
PE 0 KE 0
c) After the ball is kicked, does the energy increase or decrease as the ball gets higher?
PE INC KE DEC
d) What kind of energy is at a maximum when the ball is finished rising and is just about to start falling?
PE MAX
e) What kind of energy is at a maximum when the ball is hitting the ground?
KE MAX
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