11) What are the coefficients in front of NO 3 - ( aq ) and Cu( s ) when the fol

Question

11)

What are the coefficients in front of NO3-(aq) and Cu(s) when the following redox equation is balanced in an acidic solution:
___ NO3-(aq) + ___ Cu(s) ___ NO(g) + ___ Cu2+(aq)?

Select one:

A. 3, 6

B. 2, 6

C. 2, 3

D. 3, 4

12)

The values of H°f for the three states of benzene are approximately -22 kcal/mol, -11 kcal/mol, and 20kcal/mol. Which is the value for solid benzene?

Select one:

A. -22 kcal/mol

B. 20 kcal/mol

C. -11 kcal/mol

D. cannot be determined without additional information

13)

Calculate the total quantity of heat required to convert 25.0 g of liquid CCl4(l) from 35.0°C to gaseous CCl4 76.8°C (the normal boiling point for CCl4)? The specific heat of CCl4(l) is 0.857J/gC its heat of fusion is 3.27kj/mol and its heat of vaporization is 29.82kJ/mol.

Select one:

A. 1.43 kJ

B. 6.28 kJ

C. 5.74 kJ

D. 0.896 kJ

18)

When heated, mercury(II) oxide decomposes into elemental mercury and oxygen:
2 HgO(s) 2 Hg(l) + O2(g) H° = 181.6 kJ S° = 216.4 J/K
Estimate the temperature at which HgO should begin to decompose if the partial pressure of O2(g) is constant at 1.00 atm.

Select one:

A. 840°C

B. -34.8°C

C. 34.8°C

D. 566°C

19)

When 50.0 mL of 0.400 M Ca(NO3)2 is added to 50.0 mL of 0.800 M NaF, CaF2 precipitates, as shown in the net ionic equation below. The initial temperature of both solutions is 25.00°C. Assuming that the reaction goes to completion, and that the resulting solution has a mass of 100.00 g and a specific heat of calculate the final temperature of the solution.
Ca2+(aq) + 2 F-(aq) CaF2(s) H° = -11.5 kJ

Select one:

A. 24.45°C

B. 26.10°C

C. 26.65°C

D. 25.55°C

Explanation / Answer

11.3Cu + 2NO3- + 8H+ >> 3Cu2+ + 2NO + 4H2O The correct answer is 3,2 ( Correct answer is not available in the options)

2. the delHf for liquid and solid Benzene are -ve while that of solid Benzne is positive. Hence the answer is 20 Kcal/mole ( B is the correct answer)

13.

Sensible heat required ( from35 deg.c to 76.8 deg.c)=

Mass * specific heat * temperature difference = 25* 0.857*(76.8-35)=895.6 joules =0.8956 joules

Heat required for vaporizing the liquid = mass* latent heat of vaporization =

=Moles of CCl4* heat of vaporization

Moles of CCl4= mass/ molecular weight= 25/154

Heat required for vaporization= (25/154)*29.82 Kj=4.84 Kj

Total heat required= 4.84+ 0.8956 =5.736Kj ( c is the correct answer)

18.

It is known that delG =delH- T delS

For the reaction to be feasible delG =0

delH-T delS= 0

T= delH/ delS = 181.6/0.2164 K =839.2 The correct answer given is 840. ( A is the correct answer)

19.

Moles of Ca(NO3)2 = 0.4*50/1000 =0.02 moles

Moles of NaF= 0.8*50/1000 = 0.04 moles

The stoichiometric ratio of Ca+2 and F – is 2:1 which is same as that considered.

1 moles o Ca+2 gives 11.5 Kj

0.02 moles of Ca+2 gives =11.5*0.02 = 0.23 Kj =230 Joules

Mass of resulting solution is given and its specific heat is assumed to be same as that of water (not specified in the problem)

230 =100* 4.18*(t-25)

0.55 =t-25, t= 25.55 deg.c ( D is the correct answer)

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