1- A 0.920-gram sample of magnesium is allowed to burn in 0.321 g of oxygen gas. The sole product is magnesium oxide. After the reaction, no oxygen remains and 0.809 g of magnesium oxide has been formed. What mass of magnesium is left unreacted? A)0,210 g B)0,432 g C)1,408 g D) 0,111g 2- A solution contains 12.5% NaCl by mass. What mass of solution is required to obtain 1.0 x 1023 Na atoms? A)0,013 g B)30 g C)1,2 g D)95 g E)78 g 3- Crystals from evaporation of urine analyze to 22.6% phosphorus. Which compound is probably present? A)NaNH4HPO4 B)(NH4)3PO4 C) Na3PO4 D)H3PO4 E)Ca3(SO4)2 4- The material Styrofoam is made by blowing a gas into the polymer polystyrene made from styrene. Styrene has the percent composition of C 92.26% and H 7.74% and 1.99 x 1022 molecules weigh 3.44 grams. What is the molecular formula for styrene? A) C2H2 B)C4H4 C)C6H6 D) CH E) C8H8 5- To produce ferrocene one requires 2.33 g of C5H5 (65.0 g/mol) for every 1.00 g of Fe used (55.9 g/mol). What is the value of x in the formula of ferrocene: Fe ● x C5H5? A)1 B)2 C)3 D)4 E)5 6- 4,72 g of a compound of carbon, hydrogen, and silver was burned in an atmosphere of oxygen, yielding 7.95 g of CO2, 1.02 g of H2O and 3.02 g of a mixture of silver and silver oxide. Because the production of this mixture yielded an indeterminate value for the amount of silver, another sample of the compound weighing 8.12 g was reacted with a solution of NaCl, yielding 5.57 g of AgCl. What is the empirical formula of the compound? A)C5H5Ag B)C8H8Ag C)C8H5Cl D)C8H5Ag E)C5H8Ag 7- Complete combustion of a 4.10 g sample containing only propane (C3H5) and pentane (C5H12), yielded 12.42 g CO2 and 6.35 g H2O. What is the mass % propane in this sample? A)4,5 B)38 C)50 D)30 E) 80 8- How many grams of a solid mixture containing strontium chloride would one need to make 558 ml of a 0.100 M strontium chloride solution, if the solid mixture contains 58.6% strontium chloride by weight? A)6,62 g B)15,1 g C) 8,85 g D)5,19 g E)9,52 g 9- Which of the following represents a disproportionation reaction? A) Br2 + H2O → HOBr + Br- + H+ B) S + SO2 + H2O → S2O32- + 2 H+ C) HOCl + OH- → H2O + OClD) 3 S2- + 2 CrO42- + 8 H2O → 3 S + 2 Cr(OH)3 + 10 OHE) HF → H+ + F- 10- Iron in the form FeCl2 can be determined by tiration with potassium dichromate: 6FeCl2(aq) + K2Cr2O7(aq) + 14HCl(aq) → 6FeCl3(aq) + 2CrCl3(aq) + 2KCl(aq) + 7H2O(l) An iron sample of mass 0.800 g required 18.80 mL of 0.0120 M K2Cr2O7(aq) to reach the end point. How many moles of FeCl2 were in the sample? (as a practice balance the equaiton by yourself) A) 1.43 x 10-2 B) 1.35 x 10-3 C) 3.75 x 10-5 D) 2.26 x 10-4 11- Balance the following equation in basic solution: Cr3+ + O22- → CrO42- The sum of the coefficients is: A) 49 B) 53 C) 27 D) 18 E) 38 12- Balance the following equation in basic solution: KMnO4(aq) + H2S(g) → MnO2(s) + KOH(aq) + H2O(l) The sum of the coefficients is: A) 8 B) 14 C) 21 D) 17 E) 19 13- Balance the following equation in basic solution: Al(s) + O2(g) → [Al(OH)4]- The sum of the coefficients is: A) 6 B) 12 C) 21 D) 25 E)33 14- A piece of iron wire weighing 1.63 g is converted to Fe2+(aq) and requires 21.9 mL of KMnO4 solution for its titration. Balance the equation. What is the molarity of the KMnO4 solution? The reaction occurring during the titration is: Fe2+ (aq) + MnO4- (aq) → Fe2+ (aq) + Mn2+ (aq) A) 1.33 M B) 0.267 M C) 2.67 × 10-4 M D) 14,9 M E) 1.33 × 10-3 M 15- A 5,000 ml aqueous sample containing hydrogen peroxide was diluted to 25 mL and analyzed by titration with permanganate: 2MnO4- + 5H2O2 + 6H+ → 5O2 + 2Mn2+ + 8H2O The sample required 42.8 mL of 0.0175 M permanganate to reach the end point. What is the concentration of hydrogen peroxide in the original sample? A) 0,150 M B) 0,0748 M C) 0,374 M D) 0,0599 M 16- A solution of potassium permanganate was standardized by titration of a solution prepared by dissolving 0.268 g of pure sodium oxalate in approximately 25 mL of distilled water. A 31.4 mL volume of titrant was required to reach the endpoint. The reaction is 2 MnO4- + 5 C2O42- + 16 H+ → 2 Mn2+ + 10 CO2 + 8 H2O. What is the molarity of MnO4- ? A) 0,0174 M B) 0,0255 M C) 0,0348 M D) 0,0637 M E)0,159 M 17- Under conditions for which chlorine gas has an effusion rate of 2.4 × 10-6 mol sec-1, what would be the effusion rate for bromine gas, in mol/sec? A) 1,1× 10-6 B) 1,6× 10-6 C) 2,3× 10-6 D) 3,6× 10-6 E) 5,4× 10-6 18- The volume in L H2(g) (measured at 22 °C and 745 mmHg) required to react with 30.0 L CO(g) (measured at 0 °C and 760 mmHg) in the reaction 3 CO(g) + 7 H2(g) → C3H8(g) + 3 H2O(l) is: A) 63,5 L B) 74,1 L C) 77,2 L D) 70,0 L E) 33,1 L 19- A 31,4 ml sample of nitrogen gas was collected over water at 23.7 °C and a barometric pressure of 706 mmHg. What mass of nitrogen was collected? [Vapor pressure of water at 23.7 °C is 22 mmHg]. A) 39,3 mg B) 37,7 mg C) 34,6 mg D) 33,4 mg E) 32,5 mg 20- A 34,8 mL sample of nitrogen gas was collected over water at 23.7 °C and a barometric pressure of 706 mmHg. What mass of nitrogen was collected? [Vapor pressure of water at 23.7 °C is 22 mmHg]. A) 22,9 g/mol B) 38,4 g/mol C) 57,3 g/mol D) 84,2 g/mol E) 92,0 g/mol 21- A 1,37 L vessel contains He at a temperature of 24.5 °C and a pressure of 205 mmHg. A 721 mL vessel contains Ne at a temperature of 36.2 °C and a pressure of 0.185 atm. Both of these gases are placed in a 2.00 L vessel at 302 K. What is the final pressure (in atm) in the 2.00 L vessel? A) 0,253 atm B) 0,187 atm C) 0,0657 atm D) 0,455 atm E) 0,390 atm 22- Which one of the following set of quantum numbers would not be allowed? A) n = 3, ℓ = 2, mℓ = 1 B) n = 3, ℓ = 0, mℓ = 0 C) n = 3, ℓ = 3, mℓ = 1 D) n = 3, ℓ = 2, mℓ = -1 E) n = 3, ℓ = 1, mℓ = -1 23- The quantum numbers of the last electron of nickel could be: A) n = 3, ℓ = 2, mℓ = 0, ms = 1/2 B) n = 4, ℓ = 2, mℓ = 0, ms = 1/2 C) n = 3, ℓ = 1, mℓ = 0, ms = 1/2 D) n = 3, ℓ = 2, mℓ = 0, ms = 0 E) n = 3, ℓ = 2, mℓ = 1/2, ms = ½ 24- Which of the following groups of elements is least likely to enter into chemical reactions? A) Mn, Tc, Re B) F, Cl, Br C) Li, Na, K D) Pt, Os, Ir E) N, P, As 25- Which of the following elements is likely to have the largest second ionization energy? A) Na B) Mg C) Al D) Si 26- Which of the following has the smallest second ionization energy? A) Na B) Mg C) Al D) P 27- Which of the following has the greatest number of unpaired electrons? A) Cr +2 B) Ti+3 C) Co+2 D) Ni 28- Which is the correct and complete set of Lewis structures for carbonate ion? A)I B)II C)III D)IV E)V 29- Choose the groups of molecules below in which all the molecules have a net dipole moment. A) SiHCl3, O2, H2O B) HF, H2C=CH2, H2O C) HF, CH3Cl, H2O D) CCl4, HCl, NH3 E) HF, H2O, N2 30- Which of the following molecules has both an electron group geometry and a molecular geometry described as trigonal planar? A) SiH4 B) PF3 C) OF2 D) CHF3 E) BF3 31- What is the formal charge on carbon in the bicarbonate ion (HOCO2)? A) +2 B) –2 C ) +1 D) -1 E) 0 32- Which of the following compounds is the most viscous: CH3CH2OH, CH3CH2CH2CH3, HOCH2CH2OH, CH3OCH2CH3? A) CH3CH2OH B) CH3CH2CH2CH3 C) HOCH2CH2OH D) CH3OCH2CH3 E) not enough information 33- Exactly 375.0 mg of an unknown protein is dissolved in enough water to give 50.00 mL of solution and the osmotic pressure determined as 3.25 mmHg at 298 K. Estimate the molar mass of this protein. A) 42,9 g/mol B) 3,6 g/mol C) 56,4 g/mol D) 139,0 g/mol 34- An unknown compound is composed of 65.44% C, 29.07% O and 5.49% H. A sample weighing 5.34 g, when dissolved in 60.00 g H2O lowers the freezing point to -0.600 °C. What is the molecular formula of the compound? (Kf for water = 1.86 °C/m; C = 12.0, O = 16.0, H = 1.0 g/mol). A) C3H3O B) CHO C) C15H15O5 D)C5H5O5 E) none of these 35- A saline solution begins to freeze at -1.13 °C. Express the concentration of NaCl in this solution in mass %. Kf for water is 1.86 °C m-1. A) 3,48 % B)1,74 % C) 0,870 % D)17,8 % E) 8,9 % 36- Data for the reaction A + B → C are given below. Find the rate constant for this system. Experiment [A], M [B], M 1 0.030 0.060 2 0.030 0.020 3 0.060 0.060 Initial rate, M/s 2.5 × 10-5 2.5 × 10-5 10.0 × 10-5 A) 2.8×10-2 M-1s-1 B) 2.8×10-2 Ms-1 C) 2.8 ×10-2 M2s-1 D) 1.7 × 10-3 M-1s-1 E) 1.7 × 10-3 Ms-1 37- In the first order, reaction A → products, [A] = 0.400 M initially and 0.250 M after 15.0 min, what will [A] be after 175 min. A) 1.67 × 10-3 M B) 1.04 × 10-3 M C) 3,70 × 10-2 M D) 6,024 × 10-3 M E) 2,31 × 10-1 M 38- For the reaction: 2N2O5(g) → 4NO2(g) + O2(g) the rate law is: [O 2 ] = k[N2O5] t At 300 K, the half-life is 2.50 × 104 seconds and the activation energy is 103.3 kJ/mol O2. What is the rate constant at 310 K? A) 2.78 × 10-5 s-1 B) 7.29 × 10-6 s-1 C) 7.29 × 10-8 s-1 D) 3.70 × 10-5 s-1 E) 1.05 × 10-4 s-1 39- In the first order, reaction A → products, [A] = 0.400 M initially and 0.250 M after 15.0 min, at what time will [A] = 0.200 M? A) 63,9 min B) 22,1 min C) 9,62 min D) 51,0 min E)15,0 min 40- For the reaction A → products, the following data are obtained: [A] = 1.512 M, t = 0 min [A] = 1.490 M, t = 1.0 min [A] = 1.469 M, t = 2.0 min The rate constant for a first-order reaction is k = 0.00073 s-1. What is the half life for the reaction? A) 45 min B) 0,015 min C) 68 min D) 34 min E) 75 min 41- For the reaction: 2N2O5(g) → 4NO2(g) + O2(g) the rate law is: [O 2 ] = k[N2O5] t At 300 K, the half-life is 2.50 × 104 seconds and the activation energy is 103.3 kJ/mol O2. At what temperature is the halflife 400. seconds? A) 278 K B) 325 K C) 3,04 K D) 304 K E)296 K 42- For the following chemical equilibrium, Kp = 4.6 × 10-14 at 25 °C, find the value of Kc for this reaction at 25 °C. 2 Cl2(g) + 2 H2O(g) ⇔4 HCl(g) + O2(g) A) Kc = 1.9×10-15 B) Kc = 2,2×10-15 C) Kc = 1,1×10-15 D) Kc = 9,4 × 10-15 E) Kc = 4,6 × 10-15 43- Consider the following reaction occurring at 960 K: CO2(g) + H2(g) ⇔ CO(g) + H2O(g) At equilibrium, the concentrations of reactants and products are: [CO2] = 0.0400 M, [H2] = 0.0220 M, [CO] = 0.0240 M, and [H2O] = 0.0190 M. This equilibrium is perturbed by adding CO2(g) to the system such that when a new equilibrium is reached, the concentration of CO2 is 0.050 M. What is the concentration of H2(g) at this equilibrium? A) 0,05 M B) 0,482 M C) 0,462 M D) 0,300 M E) 0,0204 M 44- A saturated aqueous solution of calcium hydroxide has a pH of 12.25. What is the [Ca2+] of such a solution ? A) 0,018 B) 5.6 × 10-13 C) 2,3 × 10-5 D) 0,035 E) 8,9 × 10-3 45- A 250.0 ml sample of gaseous hydrogen bromide, measured at 22.9 °C and 0.930 atm, was dissolved in sufficient pure water to form 250.0 ml of solution. What was the pH of that solution? A) 1,42 B) 2,58 C) 3,83 D) 4,18 E) 5,68 46- A saturated aqueous solution of calcium hydroxide is approximately 0.13% calcium hydroxide, by mass, and has a density of 1.02 g ml-1. What is the pH of such a solution? A) 11,95 B) 12,25 C) 12,55 D) 12,75 E) 13,00