17.2 & 17.4 Thermochemical Equations, Hess's Law & Enthalpy

H₂ + ½ O₂ --> H₂O + 285 kJ

is an example of a(n)

• Electrical equation

• Heat equation

• Thermochemical equation

Tags

NGSS.HS-PS1-4

C+ O₂ --> CO₂ + 60kJ

what is the ΔH for the reaction?

• +60

• -60

• there is no way to know

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

How do you calculate Enthalpy of a reaction?

• ΔH = ΔH_products - ΔH_reactants

• ΔT = q / mC

• ΔG = ΔH -TΔS

• E = mc²

Tags

NGSS.HS-PS3-1

Endothermic reactions feel

• warm
• cold

Tags

NGSS.HS-PS1-4

Did you hear about the man who got cooled to absolute zero?

• He's 0K now.

• He dead.

• Can't Happen!

• Yep... another science pun I don't understand

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-4

Use the information below to determine the correct expression to calculate the enthalpy of formation of methane.
C(s)+O2(g)→CO2(g); ΔrH∘=−393.5kJ
2H2(g)+O2(g)→2H2O(l); ΔrH∘=−571.8kJ
CH4(g)+2O2(g)→CO2(g)+2H2O(l); ΔrH∘=−890.3kJ

• 394 + (2 × 286) – 891

• –394 – (2 × 286) + 891

• 891 - [ -394 + (2 x -286)]

• –394 – 286 + 891

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

(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

ΔH is the same thing as:

• temperature

• q

• m

• C

Tags

NGSS.HS-PS3-1

ΔH means:

• temperature

• calorimetry

• enthalpy

• syntropy

A positive ΔH means the reaction is:

• complete

• at equilibrium

• exothermic

• endothermic

Tags

NGSS.HS-PS1-4