Homework,1 Atoms, molecules, and ions

Student Name………………………………….. Student No. ……………………… 1- Naturally occurring neon consists of two isotopes: 20Ne and 22Ne. How many neutrons are in each isotope ? a) 20, 22 b) 21, 23 c) 10, 10 d) 11, 13 e) 10, 12

2- An elemental ion has 22 protons, 20 electrons, and 26 neutrons. Which isotope is it? a) 48Fe b) 47Fe c) 48Ti d) 48Ti2-

e) 48Ti2+

.

3- What is the name for CuS? a) copper(II) sulfide b) copper(I) sulfur c) copper(I) sulfide d) copper sulfide e) copper(II) sulfur

4- Elements belonging to which group of the periodic table form ions with a 2+ charge? a) alkaline earth metals b) Halogens c) Chalcogens d) alkali metals

5- An element in the lower left corner of the periodic table a) is either a metal or metalloid. b) is definitely a metal. c) is either a metalloid or a nonmetal. d) is definitely a nonmetal. e) is definitely a metalloid.

6- Which of the following statements is true for neutral atoms?

a) It is possible for neutral atoms of different elements to have the same number of electrons. b) The number of neutrons in a neutral atom must always equal the number of protons. c) The number of neutrons in a neutral atom must always equal the number of electrons. d) It is possible for neutral atoms of different elements to have the same number of neutrons. e) It is possible for neutral atoms of different elements to have the same number of protons.

7- Which of the following compounds would you expect to be molecular and not ionic? a) KCl (potassium chloride, a dietary salt substitute) b) TiO2 (titanium dioxide, formed in skywriting) c) ZnS (zinc sulfide, used in photo-sensors) d) SiC (silicon carbide, an abrasive) e) CaO (calcium oxide, an acid-neutralizing agent)

8- Which one of the following is named correctly? a) Ca(HS)2, calcium sulfide b) HBrO2, bromic acid c) AlN, aluminum nitride d) FeO, iron(III) oxide e) NH4+, ammonia

9- Which of these acids has a name that begins with hydro-? a) HCl b) HClO c) HClO2

d) HClO3

e) HClO4

10- Which of the following compounds is not a possible ionic compound? a) CsCl b) SrO c) GaF3

d) Cs2O e) NaF2

Homework, 2, StoichiometryStudent name………………………………….. Student no.…………………

1- Balance the following equation and indicate whether it is a combustion, combination, or decomposition reaction.

H2O2 + SO2 H2SO4

a) H2O2 + SO2 H2SO4, decomposition reaction b) 2H2O2 + SO2 H2SO4, decomposition reaction c) 2H2O2 + SO2 H2SO4, combination reaction d) H2O2 + SO2 H2SO4, combination reaction

2- Which of the following cannot be an empirical formula? a) CH b) CO2

c) NO2

d) C3H6

e) H2N

3- How many atoms are present in 5.54 g F2? b. 8.78 1022 atoms a. 1.76 1023 atoms

d. 3.52 1023 atom c. 0.292 atom

4 -A compound contains only carbon, hydrogen and sulfur. When a 4.142 mg sample is burned completely in oxygen,

5.868 mg of CO2 and 3.603 mg of H2O are formed. What is the empirical formula?

d. C2H6Sc. C2H4S b. C2H5S a. CH3S2

5 -What is the largest mass of Cl2 that could be prepared from the reaction of 15.0 g of MnO2 (F. Wt. = 87) and 30.0 g of HCl (M. Wt. = 36.5) according to the following equation?

MnO2 + 4HCl MnCl2 + Cl2 + 2H2O

d. 0.82 gc. 5.8 gb. 12.2 ga. 14.6 g

6- Calculate the mass percent of nitrogen in HNO3. a) 45.2% b) 25.0% c) 22.2% d) 20.0% e) none of these

7- You are setting up a reaction between two chemicals that react according to the equation

3 A + 4 B products. If you start with 1.00 mole each of both A and B, which chemical will be in excess at the end, and by how much (assuming the reaction goes to completion)? a) A is in excess by 0.333 mol. b) B is in excess by 0.333 mol. c) B is in excess by 0.250 mol. d) Neither A nor B is in excess, because the reaction "goes to completion." e) A is in excess by 0.250 mol.

8- For the reaction Fe(CO)5 + 2PF3 + H2 Fe(CO)2(PF3)2(H)2 + 3CO, how many moles of CO are produced from a mixture of 5.0 mol Fe(CO)5, 8.0 mol PF3, and 6.0 mol H2? a) 15 mol b) 5.0 mol c) 18 mol d) 6.0 mol e) 12 mol

9- What is the percent yield of CaO in the reaction CaCO3 CaO + CO2 if 5.33 g of CaO are obtained when 10.0 g of CaCO3 are used? a) 5.60% b) 53.3% c) 64.7% d) 5.33% e) 95.1%

10- The alcohol in E85 fuel burns according to the following equation: C2H5OH + 3O2 2CO2 + 3H2O How many grams of CO2 are produced when 3.00 g of C2H5OH are burned in this way? a) 6.00 g b) 88.0 g c) 0.130 g d) 5.73 g e) 2.87 g

11- Consider the reaction C7H8 + 3HNO3 ® C7H5N3O6 + 3H2O

How many grams of HNO3 are required to react with 10.0 g of C7H8? a) 20.5 g b) 6.81 g c) 30.0 g d) 2.28 g

Homework,3Reactions in Aqueous solutions

Student name………………………………………….. Student number………………………

1- Which of the followings are nonelectrolytes in water? (i) HF (ii) ethanol, C2H5OH (iii) C12H22O11

(iv) KClO3

(v) Cu(NO3)2

a) ii and iii ( they are molecular compounds )b) i, ii, and iii c) i, iv, and v d) iii e) ii

2- Which reactions will not produce a precipitate from aqueous solution? a) AgNO3 + KI b) FeSO4 + Ba(OH)2

c) Pb(NO3)2 + Na2CO3

d) ZnCl2 + (NH4)2S e) NaBr + Al2(SO4)2 (Both AlBr3 and Na2SO4 are soluble.)

3- What volume of 0.125 M H2SO4 is required to neutralize 2.50 g of Ca(OH)2? a) 0.270 mL b) 0.135 mL c) 135 mL d) 270 mL (The neutralization requires 0.0338 moles of H2SO4.)

4- Based on the activity series, which of the following reactions will occur? (i)Al(s) + NiCl2(aq) (ii)Ag(s) + Pb(NO3)2(aq) (iii)Cr(s) + NiSO4(aq) a) i only b) ii only c) iii only d) i and ii e) i and iii (Al is more easily oxidized than Ni, and Cr is more easily oxidized than Ni.)

5- What mass of ethanol, C2H5OH, is required to produce 300. mL of a 0.500 M solution? a) 46.1 g b) 23.0 g c) 6.91 g (There are 0.150 moles of ethanol.) d) 92.1 g e) 13.8 g

6- What is the mass of the precipitate formed when 12.0 mL of 0.150 M NaCl is added to 25.00 mL of a 0.0500 M AgNO3 solution? a) 258 g b) 0.258 g c) 179 g d) 0.179 g (AgCl is the precipitate, and AgNO3 is the limiting reagent.)e) 36.0 g

7- Indicate the concentration of each ion or molecule present in a 0.25 M CaBr2 solution.

a) 0.25 M Ca2+, 0.25 M Br−

b) 0.25 M Ca2+, 0.50 M Br− (There are two times the moles of Br− compared to Ca2+.)c) 0.25 M CaBr2 d) 0.50 M Ca2+, 0.50 M Br−

e) 0.50 M Ca2+, 0.25 M Br−

8- What is/are the spectator ion(s) when a BaCl2 solution is combined with an H2SO4 solution? a) Ba2+(aq), H+(aq) b) SO4

2−(aq), H+(aq) c) Cl−(aq) d) Cl−(aq), H+(aq) (BaCl2(aq) + H2SO4(aq) BaSO4(s) + 2HCl(aq)) e) H+(aq)

9- A solution is made by mixing 30.0 mL of 8.00 M HCl, 100 mL of 2.00 M HCl, and enough water to make 200.0 mL of solution. What is the molarity of HCl in the final solution? a) 0.455 M b) 1.00 M c) 1.20 M d) 2.20 M (There are 0.240 moles in the first solution and 0.200 moles in the second.)e) 0.440 M f) 10.00 M

10- If 5.20 g of a salt are found in 0.180 L of a 0.500 M solution, how many grams would be present in 0.180 L of a 1.50 M solution?

a) 5.20 g b) 10.4 g c) 15.6 g (There is three times more of the salt in the same volume of the more concentrated solution.)d) 1.73 g e) 7.8 g

11- A solution is made of 25.0 mL of 0.250 M nitric acid and 15.0 mL of 0.500 M hydrochloric acid all diluted to 250. mL. What is the resulting concentration of the hydrogen ion?

a) 55.0 M b) 0.0800 M c) 0.0300 M d) 0.0500 M e) 0.0550 M

)Just 0.0.00625 moles of H+ are provided by the HNO3, and 0.00750 moles are provided by the HCl

Homework, 4 ThermochemistryStudent Name……………………………………….. Student No……………………….1- When heat is absorbed by the system from the surroundings, the process is said to be ____________, and the sign of q is ___________. a) endothermic, positive b) exothermic, positive c) exothermic, negative d) endothermic, negative

2- A 2.839-g sample of C2H4O was burned in a bomb calorimeter with a total heat capacity of 16.77 kJ/°C. The temperature of the calorimeter increases from 22.62°C to 26.87°C. What is the heat of combustion per mole of C2H4O? a) −61.2 kJ/mol b) −1.10 x 103 kJ/mol c) −3.93 kJ/mol d) −3.14 x 103 kJ/mol e) −8.90 x 103 kJ/mol f) −260. kJ/mol

3- The specific heat of lead is 0.13 J/g-K. How many joules of heat would be required to raise the temperature of 15 g of lead from 22°C to 37°C? a) 29 J b) −0.13 J c) 2.0 J d) 5.8 x 10−4 J

4- Which of the following changes always results in a negative E? a) The system absorbs heat and does work. b) The system absorbs heat and has work done on it. c) The system gives off heat and does work. d) The system gives off heat and has work done on it.

5- For a process in which the internal energy does not change, which of the following are possible? (i) heat > 0, work < 0 (ii) heat > 0, work > 0 (iii) heat < 0, work < 0 (iv) heat < 0, work > 0

a) ii and iv only b) i and ii only c) i and iii only d) ii and iii only e) i and iv only f) iii and iv only

6- The fuel used in spacecraft must contain as much energy per gram of material as possible. Based on this consideration only, which of the following fuels is best suited to be a spacecraft fuel? (a) dimethylhydrazine, (CH3)2NNH2 Hcombustion = −1694 kJ/mol (b) methanol, CH3OH Hcombustion = −726 kJ/mol

(c) ethanol, C2H5OH Hcombustion = −1371 kJ/mol (d) octane, C8H18Hcombustion = −5500 kJ/mol (e) ethylene glycol, C2H6O2 Hcombustion = −1190 kJ/mol

7- Use the H values for equations 1 and 2 to determine the value of H for equation 3. (1) 2NO N2 + O2 H = −180. kJ (2) 2NO + O2 2NO2 H = −112 kJ (3) N2 + 2O2 2NO2 H = ? a) −292 kJ b) 68 kJ c) −68 kJ d) 292 kJ

7- From the following enthalpies of reaction, H2(g) + F2(g) 2HF(g) H = −537 kJ C(s) + 2F2(g) CF4(g) H = − 680. kJ 2C(s) + 2H2(g) C2H4(g) H = +52.3 kJ calculate H for the reaction of ethylene with F2: C2H4(g) + 6F2(g) 2CF4(g) + 4HF(g) a) −1165 kJ b) +234 kJ c) −2486 kJ d) −1269 kJ e) −2382 kJ

8- Which of the following quantities ( heat, work, enthalpy, internal energy) depend only on the end points and not on the path followed in a process? a) heat b) work c) enthalpy and internal energy d) enthalpy e) internal energy

9- When 0.215 mol NH3 is formed from nitrogen and hydrogen, 9.91 kJ of energy is released as heat. Assuming constant pressure is maintained, what is the H for this reaction per mole of NH3 formed? a) −9.91 kJ b) 46.1 kJ c) 9.91 kJ d) −2.13 kJ e) −46.1 kJ

10- A volume of 50.0 mL of 0.400 M HBr at 24.35°C is added to 50.0 mL of 0.400 M NaOH, also at 24.35°C. The final temperature is 27.06°C. Calculate the enthalpy change, H, in kJ for the following reaction: HBr(aq) + NaOH(aq) NaBr(aq) + H2O(l) (Heat capacity of the system is 0.418 kJ/°C.) a) −324 kJ b) −28.4 kJ c) −56.7 kJ d) −113 kJ Homework, 5. Properties of solutions

............................................................ الرقم الطالبة اسم.................................. ...الجامعي

I- True or false

1-( T ) The solubility of gases in water decreases with increasing temperature.

2-( T ) A mixture of three gases is a solution of gas in gas

3-( T ) The decrease in vapor pressure of a solution, P increases when molality of non volatile solute increases.

4-( F ) The ppm concentration is usually used for large concentration solutions.

5-( T ) The hypertonic solution is the more concentrated solution

II- Choose the most correct answer

1- What is the percent CdSO4 by mass in a 1.0 molal aqueous solution (molar mass of CdSO4 = 208.46 g/mol)?

a. 0.001 % b. 0.10 % c. 17.2 % d. 20.8 %

2- When 12.1 g of the sucrose (a nonelectrolyte) are dissolved in exactly 800 g of water, the solution has a freezing point of - 0.082oC. What is the molar mass of sucrose?

Kf = 1.86oC/m.

a. 426 g/mol b. 99.2 g/mol c. 178 g/mol d. 343 g/mol

3- 0.2 g of non electrolytic solute is dissolved in 20 g of a liquid to elevate the boiling point of the liquid by 0.180C. What is the molecular weight of solute ? Kb= 4.212oC/m.

a. 117 g/mol b. 23.4 g/mol c. 202 g/mol d. 234 g/mol

4- Which of the following aqueous solutions should have the lowest osmotic pressure?

a. 0.01 M sucrose at 25oC b. 0.008 M NaCl at 25oCc. 0.012 M CaCl2 at 25oC d. 0.01 M sucrose at 50oC

5- The density of a 0.641 M solution of Pb(NO3)2 solution is 1.18 g/cm3? What is the molality of the solution?

(formula weights of Pb(NO3)2 = 331.2).

a. 0.641 b. 0.662 c. 622 d. 0.0641

6- Which of the following aqueous solutions will have the highest boiling point?

a. 0.10 m Na2SO4 b. 0.20 m glucose c. 0.10 m NaCl d. 0.10 m SrSO4

7- How many grams of ethylene glycol ( M Wt. = 62.1 )must be added to 1.0 kg of water to produce a solution that freeses at –5.0 OC. ( for water, Kf = 1.86 OC/m).

a) 35g b) 167g c) 89g d) 466g

Homework, 6. chemical kinetics

................................................................. الرقم الطالبة اسم......................................الجامعي

1- A first-order reaction has a rate constant of 3.0 ´ 10 ─ 3 s ─ 1. The time required for the reaction to be 75% complete is:

a. 95.8 s b. 201 s c. 231 s d. 462 s

2- The reaction: A + 2B ® products, was found to follow the rate law: rate = k[A]2[B].

Predict by what factor the rate of reaction will increase when the concentration of A is doubled and the concentration of B is tripled, and the temperature remains constant.

a. 5 b. 6 c. 12 d. 18

3- The activation energy for the reaction 2HI ® H2 + I2 is 184 kJ/mol. How many times greater is the rate constant for this reaction at 520oC than at 500oC?

A. 0.18 b. 0.50 c. 2.0 d. 4.0

4- At 35oC and 70oC the first order rate constants of a reaction are 2.50 x 10-5 and 3.26 x 10-3 s-1 respectively. What is the enthalpy of activation (kJ/mole)?).

a. 117 b. 127 c. 122 d. 130

5- What is the kinetic rate law for the following data:

Exp # [A] [B] Rate1 1.5 1.5 0.22 1.5 3.0 0.83 3.0 4.5 3.64 3.0 3.0 1.6

a. rate = k[A][B] b. rate = k[A]2[B] c. rate = k[A][B]2 d. rate = k[A]

6 A certain first-order reaction A ® B is 25% complete in 42 min at 25oC. What is the half-life of the reaction?

a. 21 min b. 42 min c. 84 min d. 101 min

7- The data in the table below were obtained for the reaction:2 ClO2(aq) + 2 OH-(aq) ® ClO3

-(aq) + ClO2-(aq) + H2O(1)

Exp. No. [CO2](M) [OH-](M)

Rate(M/s)

1 0.060 0.030 0.02482 0.020 0.030 0.002763 0.020 0.090 0.00828

What is the magnitude of the rate constant for the reaction?

a. 4.6 b. 230 c. 115 d. 713

Homework, 7. chemical equilibrium

..................................................... / الرقم ة الطالب اسم ................................... .الجامعي

1- For the following reactions the equilibrium constants are defined:A + 2B C K1

C D + E K2

Then for the reactionA + 2B D + E Kc

the equilibrium constant must be equal to:a.Kc = K1 + K2 b. Kc = K1/K2 c. Kc = K1 - K2 d. Kc = K1

·K2

2- Phosgene, COCl2, a poisonous gas, decomposes according to the equation:COCl2(g) CO(g) + Cl2(g)

If Kc = 0.083 at 900oC, what is Kp for this reaction?

a. 0.125 b. 6.1 c. 8.0 d. 0.16

3- For the following reaction at equilibrium in a reaction vessel, which one of the changes below would cause the Br2 concentration to decrease?

2NOBr(g) 2NO(g) + Br2(g) ΔHorxn = 30 kJ

a decrease the container volume b. remove some NO c. Increase the temperature. d. add more NOBr

4- The equilibrium constant for the following reaction is 0.28 at 900oC. A system at equilibrium has

[H2S] = 0.100 M, [H2] = 0.100 and [CH4] = 1.40 x 10-4 M. What is the [CS2]?CS2(g) + 4 H2(g) CH4(g) + 2 H2S(g)

a. 0.25 b. 0.15 c. 0.10 d. 0.050

5- Consider the reactions below. In which cases is product formation favored by increased temperature?

1) CO(g) + 3 H2(g) CH4(g) + H2O(g) Ho = -206.2 kJ 2) CO2(g) + C(s) 2 CO(g) Ho = 172.5 kJ 3) H2(g) + I2(g) 2 HI(g) Ho = -9.4 kJ 4) 3 O2(g) 2 O3(g) Ho = 285 kJ

a. 1, 3 b. 2, 4 c. 1,4 d. 2, 3

Homework, 8. Acid-base equilibra

.................................................. الرقم / ة الطالب اسم................................... .الجامعي

1- What is the OH ─ ion concentration in 5.2 10 ─ 4 M HNO3?

a. 1.9 10 ─ 11 M b. 1.0 10 ─ 7 Mc. 5.2 10 ─ 4 M d. zero

2- A 0.10 M HF solution is 8.4% ionized. Calculate the H+ ion concentration.

a. 8.4 10 ─ 3 b. 0.084 M c. 0.12 M d. 0.84 M

3- Acid strength decreases in the series HNO3 > HF > HC2H3O2 . Which of the following is the strongest base?

a. NO3─ b. C2H3O2

─ c. F ─ d. all the same

4- Hydrosulfuric acid (H2S) has K1 = 1.1 x 10-7 and K2 = 1.0 x 10-13. What is the H+ ion concentration of

a 0.10 M solution of H2S?

a. 1.0 x 10-4 b. 1.1 x 10-7 c. 3.3 x 10-5 d. 3.3 x 10-4

5- What is the ionization constant of HA if the H+ ion concentration of a 0.390 M solution is 4.52 x 10-5 M?

a. 5.24 x 10-9 b. 7.94 x 10-10 c. 4.52 x 10-4 d. 1.02 x 10-9

6- Consider the following salts. Which one(s) when dissolved in water will produce a basic solution?

1) NaNO3, 2) CH3COONa, 3) Na2CO3

a. 2 and 3 b. only 3 c. 1 and 2 d. only 2

7- What is the conjugate acid of methylamine, CH3NH2?

a. CH3NH- b. CH3NH3+ c. CH3NH2

+ d. CH3NH+

8- Which one of the following responses is true with regard to a 0.1 M solution of a strong acid HA?

a. [H+] > [A ─ ] b. the pH = 1.0c. [H+] < [A ─ ] d. the pH > 1.0

9- Calculate the pH of a 0.20 M HA solution. (Ka for HA = 7.2 10 ─ 4 )

a. 1.9 b. 1.6 c. 4.1 d. 3.110- What is the pH of a 0.1 M solution of a base that has Kb = 1 x 10-5

a. 11.0 b. 3.0 c. 8.5 d. 9.5

11- Which of the following salts will produce a basic solution when dissolved in water?

a. KClO4 b. NH4NO3 c. Li2CO3 d. Na2SO4

Homework, 9 . Additional aspects on Acid-base equilibria

.......................... ......................... الرقم الطالبة اسم................................... .الجامعي

1- Calculate the pH of a buffer solution which contains 0.25 M benzoic acid (C6H5CO2H) and 0.15 M sodium benzoate (NaC6H5CO2). Given Ka = 6.5 10 ─ 5.

a. 4.83 b. 3.97 c. 3.40 d. 4.41

2- 50.00 mL of 0.10 M HNO2 (nitrous acid) was titrated with 0.10 M KOH solution. After 25.00 mL of KOH solution was added, the pH in the titration flask will be: Given Ka = 4.5 10 ─ 4

a. 2.17 b. 3.35 c. 2.41 d. 8.9

3- The Ksp value for PbCl2 is 2.4 10 ─ 4. What is the molar solubility of PbCl2?

a. 2.4 10 ─ 4 mol/L b. 6.2 10 ─ 2 mol/Lc. 7.7 10 ─ 3 mol/L d. 3.9 10 ─ 2 mol/L

4- The solubility of BaCrO4 (formula weight = 253.3) is 3.5 x10-3 g/L. What is the Ksp?

a. 3.0 x 10-8 b. 1.9 x 10-10 c. 1.4 x 10-5 d. 1.9 x 10-5

5- What is the pH of a buffer solution that is 0.211 M in lactic acid and 0.111 M in sodium lactate? The Ka of lactic acid is 1.4 × 10 ─ 4

a. 5.48 b. 3.57 c. 4.13 d. 10.43