Chemistry Exam 2 Review

Calculate the work, w, gained or lost by the system when a gas expands from 15 L to 45 L against a constant external pressure of 1.5 atm. (101.3 J = 1 L · atm) A) +4.6 kJ B) -4.6 kJ C) -4.2 kJ D) -6.8 kJ E) +6.8 kJ

-4.6 kJ

What is the energy change for a system that releases 100. kJ of heat to its surroundings and has 25 kJ of work done on it? A) 75 kJ B) -75 kJ C) 125 kJ D) -125 kJ

-75 kJ

What is the molar concentration of sodium ions in a 0.150 M Na2SO4 solution? A) 0.150 M B) 0.0500 M C) 0.0750 M D) 0.300 M E) 0.450 M

0.300 M

When FeCl3 is ignited in an atmosphere of pure oxygen, this reaction takes place 4FeCl3(s)+3O2(g)⟶2Fe2O3(s)+6Cl2(g) If 3.00 moles of FeCl3 is ignited in the presence of 2.00 moles of O2 gas, how much of which reagent is present in excess and therefore remains unreacted? A) 0.25 mol O2 remains unreacted B) 0.50 mol O2 remains unreacted C) 0.33 mol FeCl3 remains unreacted D) 0.67 mol FeCl3 remains unreacted

0.33 mol FeCl3 remains unreacted

Given the chemical equation: N2 + 3 Cl2 → 2 NCl3. On a microscopic level, what do the coefficients mean? A) 1 mole of nitrogen reacts with 3 moles of chlorine to give 2 moles of nitrogen trichloride. B) 28 g of nitrogen reacts with 213 grams of chlorine to give 241 grams of nitrogen trichloride. C) 1 molecule of nitrogen reacts with 3 molecules of chlorine to give 2 molecules of nitrogen trichloride. D) 1 atom of nitrogen reacts with 3 atoms of chlorine to give 2 atoms of nitrogen trichloride.

1 molecule of nitrogen reacts with 3 molecules of chlorine to give 2 molecules of nitrogen trichloride.

Determine whether each compound is soluble or insoluble. 1. CoCO3 2. Pb(C2H3O2)2 3. (NH4)2S 4. Hg2Cl2

1. insoluble 2. soluble 3. soluble 4. insoluble

Classify the following by the sign of ΔEUnknown node type: 1. the system contracts and the surroundings get colder 2. the system expands and the surroundings get colder 3.the system contracts and the surroundings get hotter 4. the system expands and the surroundings get hotter

1. positive 2. not enough data 3. not enough data 4. negative

Calculate the percent composition of Carbon in C2H6.

2 C + 6 H = 2 (12.01) + 6(1.008) = 30.062 (amount of the element)(atomic mass)/(total mass) x 100% 2(12.01)/30.062 = 0.799 = C = 80%

Which of the following are combination reactions? 1) CH4 (g) + O2 (g) → CO2 (g) + H2O (l) 2) CaO (s) + CO2 (g) → CaCO3 (s) 3) PbCO3 (s) → PbO (s) + CO2 (g) 4) CH3OH (l) + O2 (g) → CO2 (g) + H2O (l) A) 2 only B) 1, an 4 only C) 3 only D) 2, and 3 only E) 1, 2, and 4

2 only

When the following equation is balanced, the coefficients are________. The coefficients are in the order of I, II, III, IV C8H18 + O2 → CO2 + H2O I II III IV A)2, 3, 4, 4 B) 4, 4, 32, 36 C) 2, 25, 16, 18 D) 1, 4, 8, 9 E) 2, 12, 8, 9

2, 25, 16, 18

The Haber Reaction is: 3H2 (g) + N2 (g) ⟶ 2NH3 (g) If I react 5.25 g H2 and 25.2 g N2, what is the theoretical yield of NH3? (Use the following molar masses: NH3 = 17.03 g/mol, H2 = 2.016 g/mol, N2 = 28.02 g/mol) A)28.5 g B)88.7 g C)59.1 g D) 29.6 g

29.6 g

The reaction of A (single spheres) with B (paired spheres) is shown in the following diagram: A) 2A + 2B --> A2B2 B) A2 + 2B -->A2B2 C) 2A + B2 --> A2B2 D) 2A + 2B2 --> A2B2 E) none of the given

2A + B2 --> A2B2

What volume of a 0.540 M NaOH solution contains 15.5 g of NaOH? (Molar mass, NaOH = 40.00 g/mol) A) 209 mL B) none of the given C) 4780 mL D) 1390 mL E) 718 mL

718 mL

If a theoretical yield for a given reaction is 5.78 g and the actual yield is 4.29 g, what is the percent yield for this reaction? A)135% B)34.7% C)25.8% D) 74.2%

74.2%

How many milliliters of a 9.0 M H2SO4 solution is needed to make 0.25 L of a 3.5 M H2SO4 solution? A) 0.097 mL B) 0.64 mL C) 130 mL D) 97 mL E) 640 mL

97 mL

redox reaction

A chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction.

Define an electrolyte A) A substance that does not dissolve in water, but the resulting solution conducts electricity. B) A substance that dissolves in water to form a solution that conducts electricity. C) A substance that does not dissolve in water and the resulting solution does not conduct electricity. D) A substance that dissolves in water to form a solution that does not conduct electricity.

A substance that dissolves in water to form a solution that conducts electricity.

If 4.95 g of KCI are dissolve in 250.0 mL of water, what will the molarity of the resulting solution be? A) 0.266 M B) 19.8 M C) 0.198 M D) 0.000266 M E) 16.6 M F) 0.0166 M

A) 0.266 M

The point in an Acid-Base titration where stoichiometrically the number of moles of the base (OH-ions) added is equal to the number of moles of acid (H+ ions) present is called _________? A) Equivalence Point B) End point C) Titration point D) None of the given E) Initial Point

A) Equivalence Point

Determine the oxidizing agent in the following reaction. Ni(s) + 2 AgClO4(aq) → Ni(ClO4)2(aq) + 2 Ag(s) A) Ni B) This is not an oxidation-reduction reaction C) Ag D) Ni(ClO4)2 E) AgClO4

AgClO4

In the following redox reaction, determine which atom is oxidized and which is reduced. CH4 (g) + O2 (g) --> CO2 (g) + H2O (g) Atom Oxidized: _________ Atom Reduced:_________

Atom Oxidized: C CH4 disperses, therefore getting reduced Atom Reduced: O O2 gains electrons in process

The correct oxidation number of Cr in K2CrO4 is: A) -6 B) +6 C) -2 D) +2 E)-8 F) +8

B) +6

Calcium carbide (CaC2) reacts with water to produce acetylene (C2H2) according to the following equation: CaC2 (s) + 2H2O (g) --> Ca(OH)2 (s) + C2H2 (g). The production of 13 g of C2H2 requires consumption of ____________ g of H2O? A) 4.5 B) 18 C) 9.0 D) 4.8 x 10^2 E) 4.8 x 10^-2

B) 18

When the following equation is balanced: C3H8O3 (g) --> CO2 (g) + H2O (g) the coefficient of C3H8O3 is: A) 1 B) 2 C) 3 D) 7 E) 5

B) 2

How many grams of water, H2O, contain 1.77 x 10^19 molecules of water? A) 2.94 x 10^-5 g B) 5.30 x 10^-4 g C) 1.47 x 10^-5 g D) 1.92 x 10^43 g E) 5.87 x 10^-5 g

B) 5.30 x 10^-4 g

How many sodium atoms are in 5.23 moles of sodium carbonate, Na2CO3? A) 3.15 x 10^24 B) 6.30 x 10^24 C) 1.15 x 10^23 D) 3.34 x 10^26 E) 6.68 x 10^26

B) 6.30 x 10^24

Potassium metal and chloride gas react in a combination reaction to produce an ionic compound. What is the correct balanced equation for this reaction? A) K(s) + Cl (g) --> KCI (s) B) K(s) + Cl2(g) --> KCl2 (s) C) K2(s) + Cl2(g) -- > 2 KCI (s) D) K(s) + CI2 (g) --> KCI (s) E) 2 K (s) + Cl2 (g) --> 2 KCI (s)

B) K(s) + Cl2(g) --> KCl2 (s)

What is the best procedure to prepare0.500 L of 0.200 M solution of Li3PO4? The molar mass of Li3PO4 is 115.8 g/mol. A) weigh 23.2 g of solute and add 0.500 L of water B) weigh 11.6 g of solute and sufficient water to obtain a final volume of 0.500 L C) weigh 11.6 g of solute and add 0.500 L of water D) weigh 23.2 g of solute and add sufficient water to obtain final volume of 0.500 L.

B) weigh 11.6 g of solute and sufficient water to obtain a final volume of 0.500 L

A compound contains 40.0% C, 6.71% H, and 53.29% O by mass. The molecular weight of the compound is 60.05 amu. The molecular formula of this compound is___________. A) C2H3O4 B)C2H4O2 C)CH2O D) C4H8O4 E) CHO2

B)C2H4O2

The formula weight , in g/mol, for magnesium chlorate, Mg(CIO3)2 is: A) 132.05 B) 138.39 C) 191.21 D) 193.33 E) 221.84

C) 191.21

What is the net ionic equation for the reaction between Na2S(aq) and Pb(NO3)2(aq)? A) Na2S(aq) + Pb(NO3)2 (aq) --> 2NaNO3 (aq) + PbS(s) B) S^2- (aq) + pb^2+ (aq_ + 2No^- (aq) --> 2NO^- 3(aq) + PbS(s) C) S^2- (aq) + Pb^2+ --> PbS(s)

C) S^2- (aq) + Pb^2+ --> PbS(s)

Polar Molecule

Contains an unequal distribution of charge ex. Water

For ΔEsys to always be +, what must be TRUE? A) q=w B) -w>+q C) +w>-q D) +q > -w and +w > -q E) +q>-w

D) +q > -w and +w > -q

Assume the following reaction gets a 75.0% yield. If you want to make 558g of CH3OH, how many grams of H2 do you need if you have excess CO2? CO2 (g) + 2H2 (g) --> CH3OH (g) A) 26.3 g B) 52.7 g C) 46.8 g D) 93.6 g E) 23.4 g

D) 93.6 g

A student wants to prepare 250.0 mL of 0.1 M NaCl ( molar mass NaCl = 58.4 g/mol) solution. Which is the most appropriate? A) Add 5.84 g of NaCl to 250.0mL of H2O B) Add 1.46g of NaCl to 250.0 mL of H2O C) Dissolves 5.84 g of NaCl in 50.0mL of H2O and dilute to 250. mL D) Dissolve 1.46 g NaCl in 50 mL of H2O and dilute to 250 mL. E) None of the above

D) Dissolve 1.46 g NaCl in 50 mL of H2O and dilute to 250 mL.

If sulfur has an oxidation number of +3 in the reactant compound and 1+ in the product compound, which of the following is true about sulfur? A) Sulfur has been reduced and is therefore the reducing agent B) Sulfur has been oxidized and is therefore the reducing agent C) Sulfur has been oxidized and is therefore the oxidizing agent D) Sulfur has been reduced and is therefore the oxidizing agent

D) Sulfur has been reduced and is therefore the oxidizing agent

Which of these metals will be oxidized by the ions of cobalt? A) nickel B) tin C) copper D) iron E) silver

D) iron

Suppose you need 1000 mL of a 1.15 M HCI solution, but all you can find is a stock solution of HCI which is 12.4 M HCI. What volume of the stock solution would you need to dilute to give the desired volume of the 1.15 M HCI? A) 5.77 mL B) 173 mL C) 0.0267 mL D) 124 mL E) 92.7 mL

E) 92.7 mL (1.15 M) (1000mL)/12.4M = (12.4)V2/12.4 M

The combustion reaction CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) can be classified as a(n) A) none of the given B) aci-bse neutralization reaction C) precipitation reaction D) double displacement reaction E) oxidation-reduction reaction

E) oxidation-reduction reaction

Identify the fact that is FALSE about the law of conservation of energy. A) Energy can be transferred to different forms. B) Energy can be neither created nor destroyed. C)Energy can be transferred between the system and surroundings. D) Energy cannot be transferred from one object to another. E) Potential energy could be transferred to kinetic energy.

Energy cannot be transferred from one object to another.

T/F The maximum amount of product that can be formed in a reaction is called the percent yield.

False

T/F Oxygen gas is produced in a combustion reaction.

False

T/F Strong acids only partially dissociate in water.

False

Write the balanced neutralization reaction for when H2SO4 is added to NaOH.

H2 SO4 (aq) + 2 NaOH --> 2H2O(l) +Na2 SO4 (aq)

A solid acid HX is mixed with water. Two possible solutions can be obtained. Which of the following is true? A) In case I, HX is acting like a weak acid, and in case II, HX is acting like a strong acid B) In case I, HX is acting like a strong acid, and in case II, HX is acting like a weak acid. C) HX is not soluble in water D) In both cases, HX is acting like a weak acid. E) In both cases, HX is acting like a strong acid.

In case I, HX is acting like a strong acid, and in case II, HX is acting like a weak acid.

Limiting reactant

Is the reactant present in the smallest stoichiometric amount . - in other words, the reactant you will run out of first - Determines the amount of product formed (THEORICAL YIELD) in a chemical reaction from given mixture of reactants.

Dilution

M1V1=M2V2 Adding water to a solution in order to decrease the concentration

Which of the following pairs of aqueous solutions will form a precipitate when mixed? A) KCl + LiOH B) All of these solution pairs will produce a precipitate. C) K2CO3 + HNO3 D) MgCl2 + KOH E) K2S + HF

MgCl2 + KOH

Excess Reactant

Reactant which is not completely consumed.

Which one of the following is not true concerning automotive air bags? A) The two products of the decomposition reaction are sodium and nitrogen. B)The gas used for inflating them is oxygen. C) A gas is produced when the air bag activates. D) They are loaded with sodium azide initially. E) They are inflated as a result of a decomposition reaction.

The gas used for inflating them is oxygen.

A decomposition reaction is when one reactant produces two or more products.

True

T/F Oxidation occurs when a substance loses electrons.

True

T/F The compound CaSO4 is insoluble in water.

True

Percent Yield

Useful way to express the amount of product obtained from a reaction % yield = actual yield/theorical yield x 100%

Neutralization reaction

a reaction in which an acid and a base react in an aqueous solution to produce a salt and water

Solubility Rules

a set of rules used to predict whether an ionic compound will be soluble or insoluble in water

aqueous solution

a solution in which water is the solvent

volumetric analysis

a technique for determining the amount of a certain substance by doing a titration

net ionic equation

an equation showing only the species that actually change during the reaction.

Complete Ionic Equation

chemical equation showing all of the species as they are actually present in solution

molecular equation

chemical equation showing the complete, neutral formulas for every compound in a reaction.

Calorimeter

device used experimentally to determine the heat associated with chemical reaction

Solvent

dissolving medium

exothermic reaction

energy flows from a system to its surroundings

Endothermic Reaction

energy flows from the surroundings into a system

Heat Capacity

energy required to raise the temperature of an object by 1 C at constant pressure C= heat absorbed/increase in temperature

Hess's Law

f a process can be written as the sum of several stepwise processes, the enthalpy change (∆Hrxn) of the total process equals the sum of the enthalpy changes (∆Hrxn) of the various steps

Reduction

gain of electrons

The limiting reactant in a reaction: A) has the lowest ratio of coefficient in the balanced equation/moles available B) has the lowest coefficient in a balanced equation C) none of the given D) has the lowest ratio of moles available/coefficient in the balanced equation E) is the reactant for which you have the fewest number of moles

has the lowest ratio of moles available/coefficient in the balanced equation

What is a mole?

is the SI unit for expressing quantities of substances. 1 mole = 6.022 x 10 ^ 23

Titration

laboratory procedure where a substance in a solution of known concentration is reacted with another substance in a solution of unknown concentration.

Oxidation

loss of electrons

Specific Heat

measure per gram substance Units J / C . g or J/K . mol

Molar heat capacity

measured per mole substance units = J/C or J/L mol

Methyl alcohol (CH3OH), ethyl alcohol (CH3CH2OH), ethylene glycol (HOCH2CH2OH), and sucrose (C12H22O11) are commonly classified as: a) strong electrolytes b) bases c) acids d) nonelectrolytes e) weak electrolytes

nonelectrolytes

precipitation reaction

occurs when two aqueous solutions (solutions with soluble salts) are mixed, and an insoluble salt , precipitate separates from the solution.

equivalence point

point in the titration when H+ and OH^-

endpoint

point where the indicator changes color

Define an Arrhenius acid. A) accepts H+ ions B) an electron pair donor C) produces OH- ions in aqueous solution D) produces H+ ions in aqueous solution E) an electron pair receiver

produces H+ ions in aqueous solution

Net result

quantity of energy Δ(PE) is transferred to the surroundings through heat

A strong electrolyte

strong acid that completely dissociates in water. ex: HCI, H2SO4

Solute

substance being dissolved

Electrolyte

substance that produces a solution that can conduct electricity when it is dissolved in waster

Acid

substance that will dissolve and ionize in water to yield hydrogen ions H+ Proton donor

Base

substance that will dissolve in water to yield hydroxide ions, OH^-

Noneelectrolyte

substances that dissolve in water but do not produce any ions Ex: ethanol, table sugar

Which one of the following is a diprotic acid? A) hydrofluoric acid B) sulfuric acid C) chloric acid D) phosphoric acid E) nitric acid

sulfuric acid

Empirical Formula

the formula which gives the simplest whole number ratios of atoms of the various elements present in the molecule. It is equal to the sum of all atomic mass of all atoms in the empirical formula of the substances.

Molarity

the number of moles of solute per liter (1000mL) of solution M = amount of solute (in mol)/volume of solution (in L) Unit = mole/L

Thermochemistry

the study of energy changes that occur during chemical reactions and changes in state that involve heat

indicator

used to mark the equivalence point

A weak electrolyte

weak acid that partially or not at all dissociates in water. ex: HF, HCN, HNO2