Enthalpy Stoichiometry

Calculate ΔH when 2 moles of ethanol (C₂H₅OH) reacts with excess oxygen according to the following thermochemical equation?

• -2733.4 kJ

• -683.35 kJ

• -1366.7 kJ

• -910.67 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

The standard enthalpy changes of combustion of carbon, hydrogen and methane are shown in the table. Which one of the following expressions gives the correct value for the standard enthalpy change of formation of methane in kJ mol^–1? C(s) + 2H₂(g) → CH₄(g)

• 394 + (2 × 286) – 891

• –394 – (2 × 286) + 891

• 394 + 286 – 891

• –394 – 286 + 891

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

Given the following data: ΔH^○_f[FeO(s)] = –270kJmol^–1
ΔH^○_f [Fe₂O₃(s)] = –820 kJ mol^–1
S elect the expression which gives the enthalpy change, in kJ mol^–1, for the reaction:
2FeO(s) + 1⁄2O₂(g) → Fe₂O₃(s) 

• (–820 × 1⁄2) + 270 = –140

• (+820 × 1⁄2) – 270 = +140

• –820 + (270 × 2) = –280 

• +820 – (270 × 2) = +280 

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

ΔH is the same thing as:

• temperature

• q

• m

• C

Tags

NGSS.HS-PS3-1

If ΔH is positive, heat would be shown on the _____ side of the thermochemical equation.

• Reactant

• Product

Tags

NGSS.HS-PS1-4

C+ O₂ --> CO₂ + 60kJ, what is the value for ΔH for the reaction?

• +60

• -60

• there is no way to know

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

What will ΔH be if there is 1 mole of oxygen? 4Fe(s) + 3O₂(g) --> 2Fe₂O₃(s) ΔH = –1500 kJ

• -500 kJ

• 500 kJ

• -750 kJ

• -4500 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

What is ΔH if 2 mol of O₂(g) is reacted in this reaction? H₂(g) + ½ O₂(g) → H₂O(l) ∆H = -285.8 kJ

• -570 kJ

• -71.45 kJ

• -1143.2 kJ

• -142.9 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

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 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