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The Islamic University of Gaza General Chemistry (CHEMA 1303) Chemistry Department Time: 1 hour Date : 2.12.2007 األحد .........................................................:االسم نظام.د فخر.د ماجد. زياد د. د:المدرس 25 .................................... :الرقم الجامعي : الشعبة 101,102, 103 ***** 201, 202, 203, 204, 205 I) Indicate if the following statements are True ( T ) or False (F) ( ( ( ( ( ( ) ) ) ) ) ) (1/2 mark each) 1- Sodium sufide, Na2S is expected to dissolve in water 2- NH3 is the conjugate base of nitrous acid, HNO2 3- The oxidation number of Cr in dichromate ion Cr2O7 2- is +3 4- The reaction between Mg and HCl acid is an oxidation- reduction reaction 5- When water forms from H2 and O2 gases, E and H are equal for this reaction 6- The electron configaration of Cr ( z = 24 ) is [Ar]4s2 3d4 II) Choose the correct answer: (1 Mark each) 1. One of the followings is not a state function. a.Heat b. Enthalpy c.Internal energy d. Potential energy 2. The main device used in gravimetric analysis is a. buret b.Balance c. Flame d. Calorimeter 3- Which of the following is not a possible valu e of mℓ for an electron of ℓ = 2 a. 0 b.+3 c.-1 d.2 4. When adding 50 mL of water to 50 mL of 0.1 M NaCl solution the number of moles of NaCl will a.Increase b.Decrease c.unchanged d. None of mentioned 5. A neutral atom of the element that has atomic number 17 has _____ valence electrons a. 1 b. 3 c. 5 d. 7 6- Which of the following electron configurations represents a ground state of a neutral atom? a.[Ne] 3s1 3p1 b. [He] 2s1 2p3 c.[Ne] 3s2 3p3 d. [Ne] 3s2 3p3 3d1 III) Choose the correct answer: (Showing the solution for each) (2 Marks each) 1- The molarity of 85.0 mL solution contains 1.77g ethanol ( MWt = 46.0 ) in water is a. 0.144 M b. 0.561 M c. 0.452 M d. 6.174 M 2- The density of a gaseous compound is 3.38 g/L at 40oC and 1.97 atm. .So the molar mass of the compound will be, a.33.8 g/mol b.180 g/mol c.77.2 g/mol d. 44.1 g/mol 3- When a 25.0-g block of aluminum absorbs 10.0 kJ of heat, its temperature will rise how many degrees? The specific heat of Al is 0.900 J/ºC.g a. 444oC b. 225oC c. 22.5oC d. 360oC 4- If 1.0 L of H2 gas was mixed with 1.0 L O2 gas at 120oC and 1.0 atm., the volume of water vapor produced at the same conditions will be, a.1.0 L b.2.0 L c.3.0 L d.1.5 L 2 5- For the reaction, N2 (g ) 3 H2 (g) 2 NH3 (g) H = - 92.6 kJ 4 so, heat released when 1.26 x 10 g NH3 produced at constant pressure will be as a. – 185.2 kJ b. – 2.24 x 103 kJ c. – 3.43 x 104 kJ d. – 1.24 x 104 kJ 6- How many molecules of O2 are there in 1.0 L air at STP ? O2 is 21% of air by volume ( Avog. No. = 6.022 x 1023 ) a. 2.2 x 1020 b. 3.24 x 1019 c. 5.65 x 1021 d. 1.24 x 1041 7- If a compound A, converts to compound B with H = - 10 kJ, and compound B, converts to compound C with H = - 20 kJ, then if compound C, converts to A, so H of this change will be a. – 10 kJ b.+ 10 kJ c. – 30 kJ d. + 30 kJ 8- Balance the following equation, then write the ionic and net ionic equations Mg(NO3)2 (aq) + NaOH(aq) Mg(OH)2 + NaNO3 3 1- If a compound A, converts to compound B with H = - 10 kJ, and compound B, converts to compound C with H = - 20 kJ, then if compound C, converts to A, so H of this change will be 2- When a 25.0-g block of aluminum absorbs 10.0 kJ of heat, its temperature will rise how many degrees? The specific heat of Al is 0.900 J/ºC.g 4