GASES
List all the equations used in gas laws and solve this problem:
1) A fixed amount of oxygen gas is held in a 1.00-L tank at a pressure of 3.50 atm. The tank is connected to an empty 2.00-L tank by a tube with a valve. After this valve has been opened and the oxygen is allowed to flow freely between the two tanks at a constant temperature, what is the final pressure in the system?
Boyles law: P1V1=P2V2, Charles' Law: V1/T1=V2/T2, Gay-Lussac’s Law: P1/V1, Combined Gas law: (V1P1)/T1=(V2P2)/T2
ANSWER TO QUESTION: 1.17 atm
1. When gasoline is burned in an automobile engine, what evidence indicates that a chemical change has occurred?
2. Under what conditions does a precipitate form in a chemical reaction?
3. When reactions occur in aqueous solutions what common types of products are produced?
1. change in temp, gases formed
2. if at least one possible new product is insoluble in water
3. precipitate, water, or a gas
1) A substance is analyzed in the laboratory and found to contain 20.23 g of aluminum and 79.77 g of chlorine. What is its empirical formula? (hint: convert the grams of each element to moles first.)
2) What is the empirical formula for a compound that is 40.0% C, 6.7% H, and 53.5% O by mass?
3) A sample of an unknown hydrocarbon was found to contain 8.56 g of carbon and 1.44 g of hydrogen. Its molar mass was found to be 28.03 g/mol. What is the hydrocarbon’s molecular formula?
1) AlCl3
2) CH2O
3) C2H4
1) *Reaction: N2(g) + 3 H2(g) ⮀ 2 NH3(g); NH3 added
2) Reaction: H2(g) + I2(g) ⮀ 2 HI(g); H2 added
3) Reaction: CO(g) + H2O(g) ⮀ CO2(g) + H2(g); H2O added
4) *Reaction: 2 SO2(g) + O2(g) ⮀ 2 SO3(g); SO3 added
5) Reaction: 2 SO2(g) + O2(g) ⮀ 2 SO3(g); SO2 added
6) Reaction: 2 NCl3(g) ⮀ N2(g) + 3 Cl2(g); NCl3 added
1) left
2) right
3) right
4) left
5) right
6) right
carbonate
sulfate
sulfite
phosphate
CO32-, SO42-, SO32-, PO43-
What are the Properties of Gases?
“Ideal” gases have those properties according to the tenets of Kinetic-Molecular Theory:
Properties of Gases:
1. Gases have an indefinite shape.
2. Gases have low densities.
3. Gases can be compressed.
4. Gases will expand to fill their container.
5. Gases mix completely with other gases in the
same container.
Kinetic-Molecular Theory:
-Gases are made up of very tiny molecules (particles have negligible volume).
– Gas molecules demonstrate rapid motion in straight lines and in random directions.
– Gas molecules have no attraction for one another.
– Gas molecules undergo perfectly elastic collisions.
– The average kinetic energy of gas molecules is proportional to the Kelvin temperature: K.E. ∝ T.
1. You find a bottle in the lab that contains a white solid. The handwriting on the label is unclear, and might say barium chloride, lead chloride, or zinc chloride. When you transfer a sample of the solid to a beaker and add water, the solid dissolves. When you then add a few drops of sodium sulfate solution, a solid precipitate forms. What is the identity of the badly labeled white solid?
2) A piece of aluminum metal is placed in an aqueous solution of KCl. Another piece of aluminum is placed in an aqueous solution of AgNO3. Explain why a chemical reaction does or does not occur in each instance.
1) barium chloride
2) Al does not react with KCl solution because Al is below K on the activity series; Al reacts with AgNO3 solution because Al is above Ag on the activity series
1) Write and balance an equation for aluminum metal (Al(s)) reacting with a solution of hydrochloric acid (HCl(aq)).
2) If you begin with 0.317 moles of aluminum that react with excess hydrochloric acid, how many grams of hydrogen gas form?
3) If 4.25 g of aluminum chloride are formed during the reaction, what mass of hydrochloric acid must have reacted?
1) 2Al(s) + 6HCl(aq)→2AlCl3(aq) + 3H2(g)
2) 0.959 g H2
3) 3.49 g HCl
1) *What is the concentration of hydroxide ion in saturated limewater if the hydronium ion concentration is 3.98 x 10-13 M? Is the limewater solution acidic, basic or neutral?
2) What is the concentration of hydronium ions in a 0.1M ammonia solution if the concentration of hydroxide ions in the solution is 1.26 x 10-3 M? Is the ammonia solution acidic, basic, or neutral?
3) What is the concentration of hydroxide ions in a 0.1M borax solution if the hydronium ion concentration is 6.31 x 10-10 M? Is the solution acidic, basic, or neutral?
1) [OH−] = 2.51 x 10-2 M; basic
2) [H3O+] = 7.94 x 10-12 M; basic
3) [OH−] = 1.58 x 10-5 M; basic
Why did the electron stay home from school?
It was feeling a little negative.
1) State Avogadro’s principle in your own words.
2) What is standard temperature and pressure (STP)?
3) What is the molar volume of any gas at STP?
1) equal volumes of gas at the same T and P contain equal nos. of particles
2) 0°C, 1 atm
3) 22.4 L
1) The enthalpy change for a reaction, delta H, is exergonic. What does this indicate about the chemical potential energy of the system before and after the reaction? (Draw graphs for both exergonic and endergonic)
2) Identify the substance that is oxidized in this reaction: 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
3) The oxidation numbers of the elements in CuSO4 are respectively:
A. +2, +6, ─2
B. +3, +5, ─2
C. +2, +2, ─1
D. +2, 0, ─2
1) system’s CPE is less after reaction than before
2) N
3) a
1) If 150. grams of H2O (l) decomposes due to an electric current, what volume of O2 (g) forms at STP? If only 90.1 L of oxygen gas are actually produced, what is the percent yield?
2) Aluminum is placed in a solution of sulfuric acid (H2SO4). If 15.0 mL of 0.500 M H2SO4 reacts, how many grams of Al (s) react? What volume of H2 (g) at 28°C and 1.89 atm forms?
1) 93.2 L O2 ; 97%
2) 0.135 g Al ; 0.0980 L H2
1) How would increasing the volume of the reaction vessel affect these equilibria?
a. NH4Cl(s) ⮀ NH3(g) + HCl(g)
b. N2(g) + O2(g) ⮀ 2 NO(g)
2) Keq = 1.60 at 933K for the following reaction: H2(g) + CO2(g) ⮀ H2O(g) + CO(g); Calculate the equilibrium concentration of hydrogen when [CO2] = 0.320M, [H2O] = 0.240M, and [CO] = 0.280M.
1)
a. shifts to right
b. no shift
2)[H2] = 0.131M
hydrogen carbonate
hydroxide
nitrate
nitrite
HCO3-, OH-, NO3-, NO2-
Do these gas law problems:
1) Determine the number of atoms in 56.1 moles of aluminum
2) Hot-air balloons rise because the hot air inside the balloon is less dense than the cooler air outside. Calculate the volume an air sample will occupy inside a balloon at 43.0°C if it occupies 2.50 L at the outside air temperature of 22.0°C, assuming the pressure is the same at both locations.
3) A weather balloon is filled with helium that occupies a volume of 5.00 x 104 L at 0.995 atm and 32.0°C. After it is released, it rises to a location where the pressure is 0.720 atm and the temperature is −12.0°C. What is the volume of the balloon at that new location?
1) 3.38 x 1025 atoms of Al
2) 2.68 L
3) 5.91 x 104 L
1) Write AND balance skeleton equations for the following reactions.
a. ammonium phosphate(aq) + chromium(III) bromide(aq) → ammonium bromide(aq) + chromium(III) phosphate(s)
b. chromium(VI) hydroxide(s) → chromium(VI) oxide(s) + water(s)
c. aluminum (s) + copper(I) chloride(aq) → aluminum chloride(aq) + copper(s)
1)
a. (NH4)3PO4(aq) + CrBr3(aq) → 3NH4Br(aq) + CrPO4(s)
b. Cr(OH)6(s) → CrO3(s) + 3H2O(l)
c. Al(s) + 3CuCl(aq) → AlCl3(aq) + 3Cu(s)
1) If 5.50 moles of hydrochloric acid (HCl (aq)) react with 2.50 moles of magnesium metal, how many moles of hydrogen gas will form?
2) If 4.30 grams of sodium chloride react with 8.34 grams of silver nitrate, how many moles of precipitate will form?
3) Given the reaction and amounts in #2, how many grams of excess reactant will remain?
1) 2.50 moles H2
2) 0.0491 moles AgCl
3) 1.43 g NaCl
1) Solution A has a pH of 2.0. Solution B has a pH of 5.0. Which solution is more acidic? Based on the hydronium ion concentration in the two solutions, how many times more acidic?
2) If the concentration of hydronium ions in an aqueous solution decreases, what must happen to the concentration of hydroxide ions? Why?
3) Write a balanced equation for the reaction between sulfuric acid and calcium metal.
1) Solution A is 1000 times more acidic than solution B
2) [OH−] increases because the product of [H3O+] and [OH−] is a constant, Kw
3) H2SO4(aq) + Ca(s) → CaSO4(aq) + H2(g)
What did the scientist say when he found two isotopes of helium?
HeHe
1) The lowest pressure achieved in a laboratory is about 1.0 x 10-15 mm Hg. How many molecules of gas are present in a 1.00-L sample at that pressure and a temperature of 22.0°C?
2) Which of the following is/are possible identities for a gas that has a mass of 71.7 at a pressure of 2.50 atm, a temperature of 0°C, and a volume of 10.0 L? oxygen gas, sulfur dioxide gas, C2H5Cl, chlorine gas
3) If a snowflake contains 1.9 x 1018 molecules of water, how many moles of water does it contain?
1) 3.3 x 104 molecules
2) SO2, C2H5Cl – both have molar masses very close
3) 3.2 x 10-6 moles H2O
1. Which of these equations does not represent a redox reaction? Explain your answer.
A. LiOH(aq) + HNO3(aq) → LiNO3(aq) + H2O(l)
B. Ag(s) + S(s) → Ag2S(s)
C. MgI2(aq) + Br2(aq) → MgBr2(aq) + I2(aq)
2. Identify the following as endothermic (endergonic if energy is not thermal energy) or exothermic (exergonic if energy is not thermal energy) processes/reactions:
a. Burning a candle
b. Melting ice
c. Condensing water vapor
d. Nail polish that changes color in the sun
1. A – oxidation numbers do not change
2. a. exothermic
b. endothermic
c. exothermic
d. endergonic
1) Many compounds have the ability to incorporate water into their crystal structure. CoCl2 is an anhydrous blue compound. In the presence of water (from moisture in the air) CoCl2 forms CoCl2⋅6H2O, a hydrated red compound containing six waters of hydration per CoCl2 unit. This particular property of CoCl2 is put to use in many home hygrometers used to indicate high or low air humidity: CoCl2 (blue on dry days) becomes CoCl2⋅6H2O (red or pink on humid days). (a) Write a balanced equation for the hydration of cobalt(II) chloride. (b) If a hygrometer is made up using 1.0 g of cobalt(II) chloride what mass of water will the hygrometer pick up on a very humid day?
1)
a. CoCl2(s) + 6H2O(l) → CoCl2∙6H2O(s)
b. 0.83 g H2O
1) Analysis of a sample of maple syrup reveals that the concentration of hydroxide ions is 5.0 x 10−8M. What is the pH of this syrup? Is it acidic, basic, or neutral?
2) The hydroxide ion concentration in a sample of vinegar is 7.94 x 10−12M. What is the pH of the vinegar, and is it acidic, basic, or neutral?
3) *Solution A has a pH of 2.0 and solution B has a pH of 5.0; which solution has a greater hydronium ion concentration? ________ Solution C has a pH of 9.5 and solution D has a pH of 12.3; which solution has a greater hydronium ion concentration? ________
1) pH = 6.70; acidic
2) pH = 2.900; acidic
3) A; C
silver
zinc
ammonium
acetate
Ag+, Zn2+, NH4+, CH3COO-