Amounts of substance
Balance the following chemical reaction:
P4 (𝑠)+Cl2 (𝑔)⟶PCl3 (𝑙)
P4 (𝑠)+ 6Cl2 (𝑔)⟶ 4PCl3 (𝑙)
Given the following half-reaction, was the atom oxidized or reduced?
Fe4+ + 4e- --> Fe0
Iron was reduced because it gained electrons.
Sometimes leaving a bicycle in the sun on a hot day will cause a blowout (popped tire). Why?
As temperature increases, the pressure of the gas inside the tire increases and can go beyond the pressure the wall of the tire can sustain.
Can the speed of a given molecule in a gas double at constant temperature? Explain your answer.
Yes. At any given instant, there are a range of values of molecular speeds in a sample of gas. Any single molecule can speed up or slow down as it collides with other molecules. The average speed of all the molecules is constant at constant temperature.
Calculate the heat capacity in J/oC of 28.4 g of water. (Specific heat of water = 4.18 J/goC)
119 J/oC
Write a balanced chemical equation for the described reaction and identify the type of reaction:
Aqueous solutions of phosphoric acid and potassium hydroxide react to produce aqueous potassium dihydrogen phosphate and liquid water.
H3PO4 (aq) + KOH (aq) --> KH2PO4 (aq) + H2O (l)
Acid Base Reaction
Identify which atoms are oxidized and reduced in the following equation:
PCl3(𝑙)+Cl2(𝑔)⟶PCl5(𝑠)
2Cl goes from 0 to -1 (reduced)
P goes from +3 to +5 (oxidized)
Iodine, I2, is a solid at room temperature but sublimes (converts from a solid into a gas) when warmed. What is the temperature (degrees C) in a 73.3-mL bulb that contains 0.292 g of I2 vapor at a pressure of 0.462 atm?
85.5 degrees C
Describe what happens to the average kinetic energy of ideal gas molecules when the conditions are changed as follows: The average speed of the molecules is increased by a factor of 2.
Average kinetic energy would increase by a factor of 4.
How much will the temperature of a cup (180 g) of coffee at 95 °C be reduced when a 45 g silver spoon (specific heat 0.24 J/g °C) at 25 °C is placed in the coffee and the two are allowed to reach the same temperature? Assume that the coffee has the same density (1g/mL) and specific heat (4.18 J/goC) as water.
The temperature of the coffee will drop 1 degree.
What is the mass of Mg(s) required to react with 5.00 g of HCl(l) and produce MgCl2(s) and H2(g).
Mg(s) + 2HCl(l) --> MgCl2(s) + H2(g)
1.67 g of Mg
Balance the following half-reaction:
Hg(𝑙)+Br-(𝑎𝑞)⟶HgBr42-(𝑎𝑞)
Hg(𝑙) + 4Br-(𝑎𝑞) ⟶ HgBr42-(𝑎𝑞) + 2e-
(Note: acidic/basic conditions do not matter since we are not dealing with H+ ions)
A balloon with a volume of 100.21 L at 21 °C and 0.981 atm is released and just barely clears the top of Mount Crumpit in British Columbia. If the final volume of the balloon is 144.53 L at a temperature of 5.24 °C, what is the pressure (atm) experienced by the balloon as it clears Mount Crumpet?
0.64 atm
Which of the following gases diffuse more slowly than neon? F2, N2O, C2H2, NO, Cl2, H2S
All of them
Dissolving 3.0 g of CaCl2(s) in 150.0 g of water in a calorimeter at 22.4 °C causes the temperature to rise to 25.8 °C. What is the approximate amount of heat involved in the dissolution, assuming the specific heat of the resulting solution is 4.18 J/g °C? Is the reaction exothermic or endothermic?
−2.2 kJ; The heat produced shows that the reaction is exothermic.
What volume of a 0.2089 M KI solution contains enough KI to react exactly with the Cu(NO3)2 in 43.88 mL of a 0.3842 M solution of Cu(NO3)2?
2Cu(NO3)2 + 4KI ⟶ 2CuI + I2 + 4KNO3
161.4 mL KI solution
Complete and balance the following half-reaction:
H2(𝑔)⟶H3O+(𝑎𝑞) (in acidic solution)
H2(g) + H2O(l) --> H3O+(aq) + H+(aq) + 2e-
What is the density of laughing gas, dinitrogen monoxide, N2O, at a temperature of 325 K and a pressure of 113.0 kPa? (101,325 Pa = 1 atm)
1.84 g/L
A balloon filled with helium gas takes 6 hours to deflate to 50% of its original volume. How long will it take for an identical balloon filled with the same volume of hydrogen gas (instead of helium) to decrease its volume by 50%?
4.2 hours
When 1.42 g of iron reacts with 1.80 g of chlorine, 3.22 g of FeCl2(s) and 8.60 kJ of heat is produced. What is the enthalpy change for the reaction when 1 mole of FeCl2(s) is produced?
ΔH = −338 kJ
Citric acid, C6H8O7, a component of jams, jellies, and fruity soft drinks, is prepared industrially via fermentation of sucrose by mold. The equation representing this reaction is
C12H22O11 + 3O2 ⟶ 2C6H8O7 + 3H2O
What mass (kg) of citric acid is produced from exactly 1 metric ton (1.000x103 kg) of sucrose if the yield is 92.30%?
1036 kg of C6H8O7
Balance the following redox reaction:
HBrO(𝑎𝑞)⟶Br-(𝑎𝑞)+O2(𝑔) (in base)
2HBrO(aq)+2OH-(aq)-->2Br-(aq)+2H2O(l)+O2(g)
Most mixtures of hydrogen gas with oxygen gas are explosive. However, a mixture that contains less than 3.0 % O2 is not. If enough O2 is added to a cylinder of H2 at 33.2 atm to bring the total pressure to 34.5 atm, is the mixture explosive?
Yes, the percentage of O2 in this mixture is 3.8%
A 1-L sample of CO initially at STP is heated to 546 K, and its volume is increased to 2 L. What is the effect on the average kinetic energy of the molecules?
The average kinetic energy doubles.
Calculate ΔH for the process: N2(𝑔)+2O2(𝑔)⟶2NO2(𝑔) from the following information:
N2(𝑔) + O2(𝑔) ⟶ 2NO(𝑔) Δ𝐻=180.5kJ
NO(𝑔)+12O2(𝑔)⟶NO2(𝑔) Δ𝐻=−57.06kJ
66.4 kJ