Enthalpy

If the enthalpy ter (ΔH) is negative the reaction is ____.

• Endothermic
• Exothermic
• Neutral

Tags

NGSS.HS-PS1-4

The potential energy diagram of a reaction is shown. Which statement below is correct relating to this reaction?

• #1 represents the enthalpy change for this exothermic reaction.

• #2 represents the enthalpy change for this endothermic reaction.

• #3 represents the enthalpy change for this endothermic reaction.

• #4 represents the enthalpy change for this exothermic reaction.

Tags

NGSS.HS-PS1-4

In an endothermic reaction the system is releasing energy.

• True
• False

What is the Heat of Reaction  $\Delta H$  for this reaction?

• -200 KJ

• 200 KJ

• 400 KJ

• -300 KJ

Tags

NGSS.HS-PS1-4

What type of reaction is this?

• Exothermic

• Endothermic

• Energy Producing

• No way to tell

Tags

NGSS.HS-PS1-4

Endothermic reactions feel

• warm
• cold

Tags

NGSS.HS-PS1-4

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 formation of C(s), H₂(g) and C₄H₉OH(l) (in kJmol^-1) are as follows

C(s) ∆H=a

H₂(g) ∆H=b

C₄H₉OH(l) ∆H=c

What is the enthalpy change for the reaction shown below?

4C(g) + 5H₂(l) + ½O₂(g) -> C₄H₉OH(l)

• c – 4a + 5b

• 4a + 5b - c

• 2a + 10b - c

• 2a + 5b + c

Tags

NGSS.HS-PS1-4

(Hess's Law)Calculate the ∆H for the following reaction: 2H₂O₂ →  2H₂O  + 1 O₂ 
You are given these two equations:
2H₂  +  O₂ → 2H₂O            ∆H  =  -572 kJ
H₂  +  O₂  →  H₂O₂            ∆H  =  -188 kJ 

• ∆H  =  -948 kJ 
• ∆H  =  -196 kJ 
• ∆H  =  -384 kJ 
• ∆H  =  -188 kJ 

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

How do you calculate the Enthalpy of Reaction?

• ΔH = ΔH_products - ΔH_reactants

• ΔG = ΔH -TΔS

• ΔT = q / mC

• E = mc²

Tags

NGSS.HS-PS1-4