Hess's Law and Bond Enthalpies

The enthalpy change for the reaction, ∆H_r , is equal to... (pay attention to the direction of the arrow)

• ∆H₁ + ∆H₂

• ∆H₁ - ∆H₂

• -∆H₁ - ∆H₂

• -∆H₁ + ∆H₂

Tags

NGSS.HS-PS1-4

Hess's Law states that...

• all reactions are reversible

• the enthalpy change of a reaction is independent of the route taken

• the direct route results in a greater enthalpy change

• the indirect route results in a lower enthalpy change as energy is lost in the second step

The Law of Conservation of Energy states:

• Energy can created or destroyed but not transformed 
• Energy cannot be created or destroyed, it can only transformed
• Energy can't be created, destroyed or transformed

Tags

NGSS.HS-PS3-4

Why is bond breaking = bond making

• The energy to break a bond = energy to make a bond

• it does not matter with bonds

• the electrons are attracted to the same nucleus

Tags

NGSS.HS-PS1-4

ΔH value in an endothermic reaction is a positive number.

• True
• False

The diagram represents which type of reaction

• endothermic
• exothermic

Tags

NGSS.HS-PS1-4

Diagram below shows the ... (pay attention to the equation)

• Standard enthalpy of combustion

• Standard enthalpy of solution

• Standard enthalpy of formation

• Standard enthalpy of reaction

Tags

NGSS.HS-PS1-4

What is the symbol for enthalpy?

• H
• S
• G
• q

Tags

NGSS.HS-PS3-1

What symbol represents Enthalpy change?

• ΔH

• ΔT

• ΔG

• ΔS

Calculate ΔH when 4.72 g of carbon reacts with excess oxygen, according to the following equation?
C + O₂ → CO₂ 
ΔH = -393.5 kJ

• -154.8 kJ
• -95.0 kJ
• -66.7 kJ
• -199.5 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1