Islamic University of Gaza - Faculty of Science - Chemistry Department CHEM1301 - Mid Exam I

Islamic University of Gaza - Faculty of Science - Chemistry Department – CHEM1301 - Mid Exam I

18/3/2012 Time 60 minutesInstructor: ……………………….

Student Name: …………………….Student I.D: ……………………..

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Atomic Masses, amu: H=1, C=12, O=16, Na=23, Al=27, S=32, K=39, P=31, Cr=52, Ca = 40,

N = 14, Hg = 200.59

Atomic Masses, amu: H=1, C=12, O=16, Na=23, Al=27, S=32, K=39, P=31, Cr=52, Ca=40, N=14, Hg=200.59

Avogadro’s Number NA = 6.022 x1023 mol–1 , R = 8.314 J mol-1-mol-1= 0.0821 L·atm/K·mol, Specific heat of water = 4.18 J/g-oC

Multiple Choice: Choose the correct answerafter Showing Work

The chemical formula for copper(II)perchlorate is:

a) CuClO4 / b) CuClO3 / c) Cu(ClO4)2 / d) Cu(ClO3)2

How many phosphorus atoms are there in 15 g of H3PO4 (M.wt.= 98)? (Avogadro΄s No.=6.022×1023)

(a) 1.5x1022 / (b) 2.9x1023 / (c) 9.2x1022 / (d) 2.8x1024

A 1.04 g of an organic compound containing only C, H and O was burned to produce 2.062 g CO2 and 0.846 g H2O.What is the empirical formula of the compound? (At.wt: C = 12, O = 16, H = 1).

a) CH2O / b) C2H4O / c) C2HO2 / d) C2H4O

Which of the following statements is true about the compounds CO2; KCl; KNO3; N2O

a) CO2is the only molecular.

b) CO2 and N2O are the only molecular.

c) KCl, KNO3, and N2O are the only ionic.

d) CO2, KNO3, and N2O are the only molecular

e) KCl is the only ionic.

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

If 4.0 moles of Li and 2.0 moles of O2 are used in the reaction 4Li + O2 2Li2O, then the limiting reactant is ______and the theoretical yield of Li2O is ______g.

a. 1.2 × 102

b. 9.0 × 101

c. 6.0 × 101

d. 3.0 × 101

For the reaction: 4Al(s) + 3O2(g)  2Al2O3(s) , when 4.6 g Al was reacted with excess oxygen; 6.8 g of product was obtained. What was the percent yield of the reaction?

(At Wt: Al =27; O=16)

a. 74 %

b. 78 %

c. 68 %

d. 134 %

The element X consists of 5 isotopes with masses 63.929, 65.926, 66.927, 67.925, and 69.925 amu and relative abundances of 48.89, 27.81, 4.110, 18.57, and 0.62 percent, respectively. The average atomic mass of X is:

a) 63.93 amu

b) 66.93 amu

c) 65.387 amu

d) 65.927 amu

e) 65.39 amu

Which reactionwill 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)3

Which is NOT an oxidation-reduction reaction?

CaBr2(aq) + H2SO4(aq)  CaSO4(s) + 2HBr(g)
2Na(s) + 2 H2O(l)  2NaOH(aq) + H2(g)
2H2(g) + O2(g)  2H2O(g)
2Al(s) + 3H2SO4(aq)  Al2(SO4)3(aq) + 3H2(g)

The correct net ionic equation for the reaction between solutions of Pb(NO3)2 and NH4Cl is?

a.Pb(NO3)2(aq) + 2NH4Cl(aq)  NH4NO3(aq) + PbCl2(s)

b.Pb2+(aq) + 2Cl-(aq) PbCl2(s)

c.Pb2+(aq) + 2NO3-(aq) + 2NH4+(aq) + 2Cl-(aq)  2NH4+(aq) + 2NO3-(aq) + PbCl2(s)

d.NH4+(aq) + NO3-(aq) 2NH4NO3

A gas is compressed in a cylinder by a constant pressure of 10 atm from a volume of 20 L to 2.0 L. Calculate the work done on the system. (1 atm L = 101.3 J)

a) 1.01  104 J b) -180 J c) 1.81  104 J d) - 1.81  104 J e) 180 J

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 C2H4(g) + 6F2(g)  2CF4(g) + 4HF(g)

a) −1165 kJ

b) +234 kJ

c) −2486 kJ

d) −1269 kJ

e) −2382 kJ

For the reaction: Pb2+(aq) + 2Cl−(aq)  PbCl2(s) H = −22.53 kJ/mol

Calculate H when 0.230 mol of PbCl2(s) is dissolved in water.

a) 5.18 kJ

b) 22.5 kJ

c) −5.18 kJ

d) −22.5 kJ

What is the final temperature of 325 g of water at 4.2oC after absorbing 12.28 kJ? specific heat of water = 4.184 J/g·oC.

a. 4.21oCb. 4.8oCc. 9.0oCd. 13.2oC

15. Calculate the internal energy change for a gaseous system confinedمحجوز in a piston.

The system absorbs heat of 150 J and moves the piston upwards making work of 80 J

a) +0.23 kJ

b) − 0.23 kJ

c) + 0.070 kJ

d) − 0.070 kJ

Part II- Solve the following problems (Showing your work)

1) If 4.0 moles of Li and 2.0 moles of O2 are used in the reaction: 4Li + O2 2Li2O

, then the limiting reactant is ______and the theoretical yield of Li2O is ______g.

(a) oxygen, 1.2 × 102 / (b) lithium, 60 / (c) oxygen, 60 / (d) lithium, 30

2) The combustion of methylhydrazine (CH6N2) produces N2(g), CO2(g), and H2O(l):

2CH6N2(l) + 5 O2(g) 2 N2(g) + 2 CO2(g) + 6 H2O(l)

When 4.00 g of methylhydrazine is combusted in a bomb calorimeter, the temperature of the calorimeter increases from 25.00 °C to 39.50 oC. Find the heat capacity of the bomb in kJ/°C, provided that the heat of reaction for the combustion of one gram of CH6N2 is 28.2 kJ/g-°C

3) How many carbon atoms are there in 200 molecules of C3H8O?

(a) 600 atoms / (b) 200 atoms / (c) 3.61 × 1026 atoms / (d) 1.20 × 1026 atoms

Part 1: Choose the correct answer for the following questions:

1)Which of these acids has a name that begins with hydro-?

(a) HCl / (b) HClO / (c) HClO2 / (d) HClO3

2) Which of the following statements is true about CO2; KCl; KNO3; N2O?

(a) CO2 is the only molecular compound.
(b) CO2 and N2O are the only molecular compounds.
(c) KCl, KNO3, and N2O are the only ionic compounds.
(d) CO2, KNO3, and N2O are the only molecular compounds.

3) Which of the following are nonelectrolytes in water?

(i) HF / (ii) C2H5OH / (iii) C12H22O11 / (iv) KClO3 / (v) Cu(NO3)2
(a) ii and iii / (b) i and ii / (c) iv and iv / (d) i and iii

4) Which reactions will not produce a precipitate from aqueous solution?

(a) NaBr + Al2(SO4)2
(b) FeSO4 + Ba(OH)2
(c) Pb(NO3)2 + Na2CO3
(d) ZnCl2 + (NH4) 2S

5) According to the first law of thermodynamics,

a) the amount of work done during a change is independent of the pathway of that change.

b) the entropy of a pure, crystalline substance at absolute zero is zero.

c) energy is conserved during any process.

d) none of these.

19) A sample of iron absorbs 67.5 J of heat where its temperature increases from 21.5 °C to 28.5 °C. If the specific heat of iron is 0.450 J/g.K, what is the mass (in grams) of the sample?

A) 21B) 11C) 4.3D) 1100

20) Which one of the following reactions where ΔH°rxn equal to the heat of formation of the product?

A) (1/2) N2(g) + O2(g) → NO2(g)B) N2(g) + 3H2(g) → 2NH3(g)

C) 6C(s) + 6H(g) → C6H6(l)D) P(g) + 4H(g) + Br(g) → PH4Br(l)

21) For the reaction: 2S(s) + 3O2(g) →2SO3(g), the value of ΔH°is -790 kJ. What is the enthalpy change (kJ) if 0.95 g of S is used in the reaction?

A) -12B) -23C) 23D) 12

22) Which combination will produce a precipitate?

A) NH4OH(aq) and HCl(aq)C) NaCl(aq) and H C2H3O2(aq)

B) NaOH(aq) and HCl(aq)D) NaOH(aq) and Fe(NO3)2(aq)

23) Given the data in the table below, what is ΔH°rxn for SO3(g) + H2O(l) →H2SO4(l)

substance / Hof (kJ/mol)
SO2(g) / -297
SO3(g) / -396
SO2Cl2(g) / -364
H2SO4(l) / -814
H2O(l) / -286

A) -132B) 1496C) 704D) -704

24) Which combination will produce a precipitate?

A) NH4OH(aq) and HCl(aq)B) NaOH(aq) and HCl(aq)

C) NaCl(aq) and H C2H3O2(aq)D) NaOH(aq) and Fe(NO3)2(aq)

25) In which reaction does the oxidation number of oxygen increase?

A) HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)B) MgO(s) + H2O(l) → Mg(OH)2(s)

C) 2SO2(g) + O2(g) → 2SO3(g)D) 2H2O(l) → 2H2(g) + O2(g)

26) What is the mass (g) of CaF2 will be formed when 47.8 mL of 0.334 M NaF is treated with an excess of aqueous Ca(NO3)2? 2NaF + Ca(NO3)2→ CaF2 + 2NaNO3

A) 0.472B) 2.49C) 0.943D) 0.623

27) How many oxygen atoms are contained in 2.74 g of Al2(SO4)3?

A) 6.02 × 1023B) 7.22 × 1024C) 5.79 × 1022D) 8.01 × 10-3

28) 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) C2H3O4B) C2H2O4C) C2H4O2D) CHO2

29) For the reaction: N2(g) + 3H2(g) →2NH3(g), the percent yield is 87.5%, how many moles of N2 are needed to produce 3.00 mol of NH3?

A) 1.00B) 1.5C) 1.71D) 2.32