Science Homework Help

***Exam – please take, only have to show work begining question 30

1.The sign of ΔH for an endothermic process is ___, because it________

Group of answer choices

negative, gives off heat to the surroundings

positive, gives off heat to the surroundings

negative, absorbs heat from the surroundings

positive, absorbs heat from the surroundings

2.The sign of ΔH for an exothermic process is ___, because it________

Group of answer choices

negative, gives off heat to the surroundings

positive, gives off heat to the surroundings

negative, absorbs heat from the surroundings

positive, absorbs heat from the surrounding

3.At constant pressure, the sign of q for the process CO2(g) => CO2(s) is____, because______

Group of answer choices

negative, the process is endothermic

positive, the process is exothermic

negative, the process is exothermic

positive, the process is endothermic

not enough information

4.At constant pressure, the sign of q for the process CH4(l) => CH4(g) is____, because______

Group of answer choices

positive, the process is exothermic

not enough information

negative, the process is endothermic

negative, the process is exothermic

positive, the process is endothermic

5.If 20.00 mol of hydrogen gas completely reacted with 20.00 mol of chlorine gas at constant pressure, releasing 3700 kJ of heat, which of the following thermochemical equations is correct?

Group of answer choices

H2(g) + Cl2(g) => 2HCl (g); ΔH° = +185 kJ

H2(g) + Cl2(g) => 2HCl (g); ΔH° = +370 kJ

H2(g) + Cl2(g) => 2HCl (g); ΔH° = –3700 kJ

H2(g) + Cl2(g) => 2HCl (g); ΔH° = -1850 kJ

H2(g) + Cl2(g) => 2HCl (g); ΔH° = –185 kJ

6.Consider the reaction:

2Fe(s) + 3/2O2(g) => Fe2O3(s); ΔHo= –824.2 kJ

Find ΔH for the following reaction.

2Fe2O3(s) => 4Fe(s) + 3O2(g)

Group of answer choices

–1648 kJ

+824.2 kJ

+3297 kJ

+1648 kJ

-3297 kJ

Flag this QuestionQuestion 72 pts

7.Considering the limiting reactant, how much heat is produced at constant pressure if 0.243 g of magnesium reacts with 100.0 mL of 0.300 M HCl according to the reaction below?

Mg(s) + 2HCl(aq) => MgCl2(aq) + H2(g); ΔHo = –462.5 kJ

Group of answer choices

6.94 kJ

9.24 kJ

4.63 kJ

13.9 kJ

23.1 kJ

8.A 0.1018 g sample of organic compound with a molar mass of 225.4 g/mol was burned in the bomb calorimeter with the heat capacity 2.95 kJ/K. The temperature in the calorimeter increased by 2.63 K. Calculate the energy of combustion of the compound in kJ/mol.

Group of answer choices

–6.62 x101

–0.0318

–0.0035

–1.78 x 102

–1.72 x 104

Flag this QuestionQuestion 92 pts

9.Which of the following equations is related to the standard enthalpy of formation of solid zinc nitrate?

Group of answer choices

Zn(s) + N2(g) + 3O2(g) => Zn(NO3)2(s)

Zn2+(aq) + 2NO3–(aq) => Zn(NO3)2(s)

Zn(s) + 2HNO3(aq) => Zn(NO3)2(s) + H2(g)

ZnO(s) + 2NO2(g) + O2(g) => Zn(NO3)2(s)

Zn(s) + 2N(g) + 6O(g) => Zn(NO3)2(s)

Flag this QuestionQuestion 102 pts

10.The following combination of signs for heat and work (respectively) represents a system that is gaining heat from the surroundings and doing work on the surroundings?

Group of answer choices

+; +

-; +

+; –

-; –

Flag this QuestionQuestion 112 pts

11.The following is correct for the chemical reaction taking place at constant pressure:

Group of answer choices

ΔH = ΔE

ΔH = ΔE + P ΔV

ΔH =w

ΔH =0

Flag this QuestionQuestion 123 pts

12.The following phase change is exothermic:

Group of answer choices

sublimation

freezing

vaporization

melting

Flag this QuestionQuestion 133 pts

13.If you remove some water from an of an ice-water mixture,

Group of answer choices

the water vapor pressure over an ice-water mixture will increase

the water vapor pressure over an ice-water mixture will decrease

the temperature of an ice-water mixture will increase

the temperature of an ice-water mixture will decrease

the temperature of an ice-water mixture will not change

Flag this QuestionQuestion 142 pts

14.The vapor pressure of a liquid will increase with the increase in the following:

Group of answer choices

the temperature of liquid

the mass of liquid

the surface of liquid

the volume of liquid

Flag this QuestionQuestion 152 pts

15.In which of the following substances the molecules will have only London dispersion forces? (Hint check the shape and polarity of the molecules)

Group of answer choices

CCl4(l)

all of the theese will have only London dispersion forces

HCl(l)

PCl3(l)

SCl4(l)

Flag this QuestionQuestion 162 pts

16.In which of the following substances the molecules will have dipole-dipole interactions as their strongest intermolecular interaction? (Hint check the shape and polarity of the molecules)

Group of answer choices

CH3Cl(l)

NH3(l)

Br2(l)

CS2(l)

Flag this QuestionQuestion 172 pts

17.In which of the following substances the molecules will not have hydrogen bonding as their strongest intermolecular interaction? (Hint check the shape and polarity of the molecules)

Group of answer choices

H2O

CH3OH

NH3OH

CH2S

Flag this QuestionQuestion 183 pts

18.The following intermolecular forces exist between the molecules of water and ethanol (CH3CH2OH):

Group of answer choices

dispersion, dipole-dipole, hydrogen bonds

dispersion, ion-dipole, hydrogen bonds, and

dispersion, dipole-dipole

dispersion, hydrogen bonds

dispersion

Flag this QuestionQuestion 193 pts

19.The following intermolecular forces exist between the particles in the aqueous solution of NaCl

Group of answer choices

dispersion, dipole-dipole

dispersion, dipole-dipole, ion-dipole, hydrogen bonds

dispersion, dipole-dipole, ion-dipole,

dispersion, dipole-dipole, hydrogen bonds

dispersion, hydrogen bonds

Flag this QuestionQuestion 202 pts

20.Which substance in the liquid state has only dipole-dipole and hydrogen bonding?

Group of answer choices

All of them

Neither – they all have also dispersion forces

ethanol

water

ammonia

Flag this QuestionQuestion 213 pts

21.The following intermolecular forces exist between the particles in the solid sulfur dioxide (check the Lewis dot structure and polarity):

Group of answer choices

dipole-dipole, hydrogen bonding

disperse

disperse, dipole-dipole

disperse, dipole-dipole, hydrogen bonding

Flag this QuestionQuestion 223 pts

22.The following is an explanation of the higher boiling of HF compared to HCl

Group of answer choices

stronger dispersion forces

stronger dipole-dipole forces

existance of hydrogen bonding

stronger covalent bonds

Flag this QuestionQuestion 232 pts

23.Which of the following pure substances has the lowest vapor pressure?

Group of answer choices

NH3

SiH4

H2Se

H2S

H2O

Flag this QuestionQuestion 243 pts

24.The value of the following will decrease with the decreasing of the strength of the intermolecular forces:

Group of answer choices

heat of fusion

vapor pressure

melting point

heat of vaporization

boiling point

Flag this QuestionQuestion 252 pts

25.On the generic phase diagram below, the gas is present at the temperatures and pressures which are the coordinates of the following points:

Group of answer choices

A, B, C, D

A, B, C, E

E, F, G

A, B, D, G

C, B, D, F

Flag this QuestionQuestion 262 pts

26.On the generic phase diagram below, the change from point E to point F describes:

Group of answer choices

melting

sublimation

vaporization

freezing

Flag this QuestionQuestion 272 pts

27.On the generic phase diagram below, the solid-gas equilibrium is represented by the segment:

Group of answer choices

A-C

B-C

A-D

B-D

A-B

Flag this QuestionQuestion 282 pts

28.On the generic phase diagram below, the equilibrium between solid, liquid and gaseous states is represented by the letter :

Group of answer choices

D

A

C

E

B

Flag this QuestionQuestion 292 pts

29.On the generic phase diagram below, ΔHovaporization is represented by the segment:

Group of answer choices

B-C

A-B

D-E

C-D

E-F

Flag this QuestionQuestion 306 pts

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30.Standard Enthalpies of Formation, in kJ/mol

N2(g) 0 NO2(g) +33.2 NH3(g) -45.9 H2O(l) -285.8

NO(g) +90.3 N2O(g) -82.1 H2O(g) -241.8

Use the data above to calculate ΔH for the reaction: (8 points)

6 NO2(g) + 8 NH3(g) => 7 N2(g) + 12 H2O(g) ΔH = ?

31.Use the standard enthalpy of formation of iron(III) chloride ( -334.0 kJ/mol) to calculate the amount of heat that will be produced by the reaction in which iron(III) chloride will be produced from 100.0 g of iron in excess chlorine gas.

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32.Use the Hess’s law to calculate the enthalpy of reaction for

3 NO2(g) + H2O(l) => 2 HNO3(aq) + NO(g)
from:

4 HNO3(aq) => 4 NO2(g) + 2 H2O(l) + O2(g) ΔH = +390.3 kJ

and 2 NO2(g) => 2 NO(g) + O2(g) ΔH = +114.2 kJ

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33.The reaction between 0. 5051g NaOH and 200.0 mL diluted sulfuric acid solution (the excess reagent) was performed in the coffee cup calorimeter:

2 NaOH(s) + H2SO4 (aq) => Na2SO4 (aq) + 2H2O(l)

Calculate ΔHrxn in kJ/molNaOH, if the temperature was raised from 22.25oC to 32.65oC.

Assume heat capacity of solution 4.182J/oC g and density of solution 1.00 g/mL

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