CHEM 177 : EXAM 2
65 Cards in this Set
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What is the oxidation number of sulfur in potassium sulfate?
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(A) 6** (B) 4 (C) 3 (D) -2
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The theoretical yield of some reaction is 14.5 g. A student runs the reaction and the mass measurement they make indicates that 15.7 g of product formed. What is the percentage yield that this student should report?
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(A) 76.4% (B) 82.7% (C) 92.4% (D) 108%**
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A concentrated, aqueous solution of ammonia is 15.0 M NH3. How many moles of NH3 are present in 15.0 mL?
e
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(A) 0.0100 mole (B) 0.100 mole (C) 0.225 mole** (D) 0.882 mol
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Based on solubility rules, which of these anions will always be a spectator ion?
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(A) CO32- (B) Cl- (C) I- (D) NO3-**
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Which process can lower the salinity of ocean waters, potentially altering ocean currents?
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(A) coral reefs using up salts that are present
(B) melting of glaciers adding more water**
(C) earthquakes causing tsunamis that mix more water
(D) plastics accumulating in water
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Which is both a base and a weak electrolyte?
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(A) NH3** (B) KOH (C) H2SO4 (D) CH3COOH
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Why does Ames have so few problems with nitrates in drinking water?
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(A) minerals in the soil precipitate nitrates
(B) minerals in the soil neutralize nitrates
(C) bacteria in the soil chemically reduce nitrates**
(D) bacteria in the soil chemically oxidize nitrates
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How is enthalpy, H, related to internal energy, E?
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(A) H = E - q (B) H = E + q (C) ΔH = mass x heat capacity x ΔE (D) H = E + PV**
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Which statement is true about a process when energy moves from the system to the surroundings?
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(A) the process is exothermic and ΔE < 0**
(B) the process is exothermic and ΔE > 0
(C) the process is endothermic and ΔE < 0
(D) the process is endothermic and ΔE > 0
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Given the equation: BaCl2(aq) + Na2SO4(aq) BaSO4(s) +2NaCl(aq) What is the net ionic equation for this reaction?
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(A) Cl-(aq) + Na+(aq) NaCl(aq)
(B) Ba2+(aq) + SO42-(aq) BaSO4(s) **
(C) Cl22-(aq) + Na22+(aq) 2NaCl(aq)
(D) BaCl2(s) + Na2SO4(s) Ba2+(aq) + 2Cl-(aq) + 2Na+(aq) + SO42-(aq)
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In the reaction, SnO2(s) + CO(g) --> Sn(s) + CO2(g) what is oxidized?
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(A) CO(g)** (B) CO2(g) (C) Sn(s) (D) SnO2(s)
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What is the concentration of ammonium ions in a 1.5 M solution of ammonium sulfate?
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(A) 0.75 M (B) 1.5 M (C) 3.0 M** (D) 4.5 M
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Which interaction could be depicted by the graph to the right?
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(A) a negative ion with a negative ion
(B) a negative ion with a positive ion**
(C) a negative ion with an electron
(D) a positive ion with a positive ion
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A system absorbs 311 J of energy as heat from the surroundings and does 202 J of work. What is the change in internal energy of the system?
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(A) -513 J (B) -109 J (C) +109 J** (D) +513 J
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Under what conditions is heat given by the change in enthalpy?
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(A) constant pressure**
(B) constant volume
(C) only gases present
(D) only solids present
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Which process can be used to remove nitrates at water treatment plants?
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(A) filtration (B) flocculation (C) ion-exchange** (D) precipitation
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Suppose you need 750. mL of a 0.450 M solution of NaOH. The stock solution you have available in the lab has a measured concentration of 2.16 M. What volume of this solution do you need to dilute to get the desired solution?
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(A) 0.729 mL (B) 1.30 mL (C) 3.60 mL (D) 156 mL**
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Which step in water treatment is responsible for killing microbes that might otherwise cause health concerns?
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(A) aeration (B) chlorination** (C) flocculation (D) fluoridation
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limiting reactant
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the reactant present in the smallest stoichiometric amount.
In other words, it's the reactant you'll run out of first
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theoretical yield
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the maximum amount of product that can be made.
In other words, it's the amount of product possible as calculated through the stoichiometry problem
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percentage yield
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(actual yield/theoretical yield)*100
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solvent
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present in greatest abundance
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solute
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everything else
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ionic compounds and water
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dissolve by dissociation, where water surrounds the separated ions
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molecular compounds
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compounds interact with water, but most do NOT dissociate.
Some molecular substances react with water when they dissolve.
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electrolyte
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is a substance that dissociates into ions when dissolved in water
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Nonelectrolyte
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may dissolve in water, but it does not dissociate into ions when it does so
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strong electrolyte
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dissociates completely when dissolved in water
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weak electrolyte
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only dissociates partially when dissolved in water
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strong electrolyte examples
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KCl, NaOH, HNO3
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weak electrolyte examples
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CH3COOH, NH3
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soluble ionic compounds
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NO3-, CH3COO-, Cl-, I-, SO4 2-
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insoluble ionic compounds
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S 2-, CO3 2-, PO4 3-, OH-
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Precipitation Reactions
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When two solutions containing soluble salts are mixed, sometimes an insoluble salt will be produced. A salt "falls" out of solution, like snow out of the sky. This solid is called a precipitate
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spectator ions
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an ion that exists as a reactant and a product in a chemical equation
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writing net ionic equations
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LOOK UP EXAMPLE PROBLEMS
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Arrhenious acid
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adds H+ ions
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Arrhenious base
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adds OH- ions
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Examples of strong acids
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HCl, H2SO4, HNO3, HBr
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Examples of strong bases
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NaOH, KOH, CaOH2
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neutralization reactions
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use acid and base to produce a salt and water
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Oil Rig
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Oxidation is loss, reduction is gain
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look up example problems of oxidation-reduction reactions
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...
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corrosion
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converts a refined metal to a more stable form, such as its oxide or hydroxide
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uniform corrosion
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most common type, proceeds uniformly over the entire exposed surface or over a large area.
The metal becomes thinner and eventually fails
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galvanic corrosion
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A potential difference usually exists between two dissimilar metals when they are immersed in a corrosive or conductive solution. If these metals are placed in contact (or otherwise electrically connected), this potential difference produces electron flow between them. Corrosion of the le…
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molarity
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a measure of the concentration of a solute in a solution
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Dilution equations
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M1V1 = M2V2
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energy
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the ability to do work or transfer heat
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heat
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Energy used to cause the temperature of an object to rise
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work
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Energy used to cause an object that has mass to move
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kinetic energy
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energy an object possesses by virtue of its motion
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potential energy
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energy an object possesses by virtue of its position or chemical composition
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system
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includes the molecules we want to study
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surrounding
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everything else
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Exothermic
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When heat is released by the system into the surroundings
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Endothermic
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When heat is absorbed by the system from the surroundings
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State function
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internal energy is a state function.
It depends only on the present state of the system, not on the path by which the system arrived at that state.
And so, E depends only on Einitial and Efinal.
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work
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w = −P*V
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change in enthalpy
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deltaH = deltaE + PdeltaV
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enthalpy definition
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a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume
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Look up enthalpy of reactions problems
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especially ones with energy release/absorption
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heat capacity
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specific heat
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calorimetry
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CHEM 177: CHAPTER 1