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

When you flip a chemical reaction using Hess's Law, what is done to the heat of reaction value?

• nothing

• the sign is flipped

• 1/delta H

Using the data below, which is the correct value for the standard enthalpy of formation for TiCl₄(l)?

• −1538 kJ mol⁻¹

• −1094 kJ mol⁻¹

• −750 kJ mol⁻¹

• +286 kJ mol⁻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

NGSS.HS-PS3-1

When you multiply a chemical equation by 2, what is done to the heat of reaction?

• multiplied by 1/2

• multiplied by 2

• nothing

For Hess' Law to be used what must be the same for all of the reactions being studied?

• The initial conditions of pressure and temperature.

• The final conditions of pressure and temperature.

• The initial and the final conditions of pressure and temperature.

• The initial and the final conditions of pressure and temperature, and the number of moles of reactants.

Consider the following reactions:Fe(s) + 1/2 O2(g) --> FeO(s) H= -272.0 kJ2 Fe(s) + 3/2 O2(g) --> Fe2O3(s) H= -825.5 kJDetermine the delta H for the reaction: 2 FeO(s) + 1/2 O2(g) --> Fe2O3

• -281.5 kJ

• -1097.5 kJ

• -1369.5 kJ

• 281.5 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

The enthalpy change for the reaction, ∆H_r , is equal to 

• ∆H₁ + ∆H₂

• ∆H₁ - ∆H₂

• -∆H₁ - ∆H₂

• -∆H₁ + ∆H₂

Tags

NGSS.HS-PS1-4

The thermochemical equation for the incomplete combustion of carbon into carbon monoxide is represented as: 2C (s) + O₂(g) --> 2CO(g) Compute for the H of the reaction if the overall process above can occur in two steps whose thermochemical equations are given below: (1) C _(s) + O_2(g) --> CO_2(g) H= -392.5 kJ (2) 2 CO_(g) + O_2(g) --> 2CO_2(g) H= -566.0 kJ

• 172.5 kJ

• 1,353 kJ

• -221.0 kJ

• 959.5 kJ

Tags

NGSS.HS-PS3-1

Determine the H for reaction of this equation: 3C (graphite) + 4 H2(g) --> C3H8(g)

using these intermediates:

C₃H₈ (g) + 5O₂(g) --> 3CO₂ (g) + 4H₂O (l) H= -2219.9 kJ

C(graphite) + O₂(g) --> CO₂ (g) H= -393.5 kJ

H₂ (g) + 1/2 O₂ (g) --> H₂O (l) H= -285.8 kJ

• -683.4 kJ

• -2899.2 kJ

• -1324.7 kJ

• -104.0 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1