Hess's Law and Bond Enthalpies

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

(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

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

• multiplied by 1/2

• multiplied by 2

• nothing

• The total pressure of the system

• The volume of the system

• The heat content of the system at constant pressure

• The total mass of the system

Tags

NGSS.HS-PS3-4

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 table of average bond energies below the image, the ΔH for the reaction in kJ is.....

• + 160 kJ

• -63 kJ

• - 160 kJ

• -217 kJ

Tags

NGSS.HS-PS1-4

The average bond enthalpies for O-O and O=O are 146 and 496 kJ/mol respectively. What is the enthalpy change, in kJ, for the reaction below? H-O-O-H(g) → H-O-H(g) + ½O=O(g)

• -102

• +102

• +350

• +394

Tags

NGSS.HS-PS1-4

For the reaction 2H₂(g) + O₂(g) → 2H₂O(g) the bond enthalpies (in kJ/mol) are H-H = x, O=O = y, O-H = z Which calculation will give the value, in kJ/mol, of ΔH for the reaction?

• 2x + y - 2z

• 4z - 2x - y

• 2x + y - 4z

• 2z - 2x - y

Tags

NGSS.HS-PS1-4

When new chemical bonds form, energy ____________.

• is taken into the system.

• is released from the system.

• stays the same in the system.

Tags

NGSS.HS-PS1-4