Hess law,lechatelier's principle

The enthalpy change for the reaction
C(s, graphite) + 1⁄2O₂(g) --> CO(g) cannot be measured directly since some carbon dioxide is always formed in the reaction.
It can be calculated using Hess’s Law and the enthalpy changes of combustion of graphite and of carbon monoxide.
C(s, graphite) + O₂(g) --> CO₂    ΔH=-394 kJmol^–1
CO(g) + 1⁄2O₂(g) --> CO₂  ΔH=-283 kJmol^–1  
The enthalpy change for the reaction of graphite with oxygen to give carbon monoxide is 

• -677 kJmol^–1 
• +111 kJmol^–1 
• -111 kJmol^–1 
• +677 kJmol^–1 

Tags

NGSS.HS-PS1-4

The enthalpies of combustion of C(s), H2(g) and C4H9OH(l) (in kJmol^-1) are as follows  
C(s) + O₂(g)   ->  CO₂(g)                                               ∆H=a
H₂(g) + ½O₂(g)   ->   H₂O(l)                                        ∆H=b
C₄H₉OH(l) + 6O₂(g)   ->   4CO₂(g) + 5H₂O(l)  ∆H=c
What is the enthalpy change for the reaction shown below?
  4C(g) + 5H₂(l) + ½O₂(g)   ->   C₄H₉OH(l)

• c – 4a – 5b
• 2a + 10b - c
• 4a + 5b - c
• 2a + 5b + c

Tags

NGSS.HS-PS1-4

Use the chart to answer the following question.
Which is correct about energy changes during bond breaking and bond formation? 

• A
• B
• C
• D

Tags

NGSS.HS-PS1-4

Changes in pressure will only affect substances that are in the __________ state.

• gaseous
• liquid
• solid
• plasma

Le Chatelier's Principle states that if a chemical system at equilibrium is stressed,

• the system will adjust to increase the stress
• the system will adjust to reduce the stress
• the system will not adjust

Tags

NGSS.HS-PS1-6

For the reaction...
SO₂ + O₂  <−>  SO₃
If the concentration of SO₂ is increased, the equilibrium of the reaction will shift ___________.

• left
• right
• left and right 
• neither left nor right

Tags

NGSS.HS-PS1-5

For the reaction...
N_{2 (g)} +  3 H_2 (g) <−> 2 NH_{3 (g)}

If the pressure in the system is increased,  which substance will increase in concentration?

• N₂
• H₂
• N₂ and H₂
• NH₃

2SO₂(g)+O₂(g)⇌2SO₃(g)
Using a catalyst

• shift equilibrium right
• shift equilibrium left
• increase rate of reaction
• have no change

Tags

NGSS.HS-PS1-5

For the reaction...
SO₂ + O₂ <−>  SO₃
If the equilibrium shifts to the right, the concentration of O₂ will ___________.

• increase
• decrease
• remain the same
• double

Tags

NGSS.HS-PS1-6

For the reaction...
heat  +  N₂  +  O₂  <−>  2NO
If the heat is added to the chemical system, the equilibrium will shift _______.

• left
• right
• left and right
• neither left nor right

Tags

NGSS.HS-PS1-5

NGSS.HS-PS1-6