CHEM120 Week 8: Exam 3 (Units 5, 6, and 7) – With 100% Correct Answers Graded A+

CHEM120 Week 8: Exam 3 (Units 5, 6,
and 7) – With 100% Correct Answers
Graded A+

Arrange the following gases in order of increasing average molecular speed at 25
°C.


Cl2, O2, F2, N2 - ANSWER---Cl2 < F2 < O2 < N2


Consider the following reaction:


2CH3OH(g) 2CH4(g) + O2(g) H=+252.8kJ


For a given sample of CH3OH, the enthalpy change during the reaction is +62.6
kJ. What is the mass of methane (CH4) gas is produced? (molar mass of
CH4=16.05g/mol) - ANSWER---7.94 g


If a reaction has a H = +369 kJ/mol, the H of the reverse reaction is - ANSWER----
369 kJ/mol


When NH4NO3(s) dissolves in water, the solution become colder. This is because
... - ANSWER---NH4NO3(s) NH4NO3(aq) is endothermic , with Hsolution > 0.


Calculate the value of internal energy (E) in joules for a system that loses 50 J of
heat and has 150J of work performed on it by the surroundings. - ANSWER---+
100

, CHEM120 Week 8: Exam 3 (Units 5, 6,
and 7) – With 100% Correct Answers
Graded A+

Given the following reactions
Fe2O3 (s) + 3CO (s) → 2Fe (s) + 3CO2 (g) ΔH = -28.0 kJ


3Fe (s) + 4CO2(s) → 4CO (g) + Fe3O4(s) ΔH = +12.5 kJ


the enthalpy of the reaction of Fe2O3 with CO
3Fe2O3 (s) + CO (g) → CO2 (g) + 2Fe3O4 (s)


is ________ kJ. - ANSWER----59.0


Of the following gases, ________ will have the greatest rate of effusion at a given
temperature. - ANSWER---He


The n = 5 to n = 3 transition in the Bohr hydrogen atom corresponds to the
________ of a photon with a wavelength of ________ nm.


1nm= 1x10-9m - ANSWER---emission, 1280


Of the following transitions in the Bohr hydrogen atom, the ________ transition
results in the emission of the highest-energy photon. - ANSWER---n = 6 → n = 4