Lesson Worksheet: Standard Enthalpy Changes Chemistry

In this worksheet, we will practice describing different types of standard enthalpy changes and defining them.

Q1:

Calculate, to the nearest whole number, the standard heat of combustion of propane (CH38), its molar mass is 44.1 g/mol, in kilojoules per mole if the change in the heat content of the complete combustion of 10 g of propane is 503.4×10 J.

  • A+2,220×10 kJ/mol
  • B+2,220 kJ/mol
  • C2,220 kJ/mol
  • D2,220×10 kJ/mol

Q2:

The following table shows the standard enthalpies of formation Δ𝐻, in kilojoules per mole, of Al(OH)3, AlO23, and Al(SO)243.

CompoundAl(OH)3AlO23Al(SO)243
The Standard Enthalpy of Formation Δ𝐻(/)kJmol1,2771,675.53,440

Which of the following statements is correct?

  • AAl(OH)3 is more thermally stable than AlO23.
  • BAl(SO)243 is more thermally stable than Al(OH)3.
  • CAl(SO)243 is less thermally stable than AlO23.
  • DAlO23 is less thermally stable than Al(OH)3.

Q3:

When a student dissolves 1 mol of a certain solute in water, the heat required to separate solvent particles is 40 kJ, the heat required to dissociate the solute particles is 80 kJ, and the hydration energy is 400 kJ. Calculate the heat of the solution and determine whether the process is exothermic or endothermic.

  • A280 kJ, exothermic
  • B+280 kJ, endothermic
  • C+520 kJ, endothermic
  • D440 kJ, exothermic

Q4:

Which of the following has the highest thermal stability?

  • ACuCl()s, which has Δ𝐻=137.2/kJmol
  • BCuSO()4s, which has Δ𝐻=771.4/kJmol
  • CCuO()s, which has Δ𝐻=157.3/kJmol
  • DCuCl()2s, which has Δ𝐻=220.1/kJmol

Q5:

After analyzing the equation below, determine which of the following represents the type of heat change accompanying this process. CaCl()+HO()Ca()+2Cl()22+2slaqaq

  • AStandard heat of combustion
  • BStandard heat of formation
  • CStandard heat of vaporisation
  • DStandard heat of solution

Q6:

After studying the given diagram, determine the sign for the value of Δ𝐻, Δ𝐻, and Δ𝐻 respectively?

  • ANegative, positive, and positive
  • BPositive, negative, and positive
  • CPositive, positive, and negative
  • DPositive, positive, and positive

Q7:

If the separation energy of ammonium nitrate in water is 150 kJ, the hydration energy is 120 kJ, and the separation energy of water is 100 kJ, then this dissolution is .

  • Aendothermic and the heat of the solution is +130 kJ
  • Bendothermic and the heat of the solution is +170 kJ
  • Cexothermic and the heat of the solution is 170 kJ
  • Dexothermic and the heat of the solution is 130 kJ

Q8:

Why is the standard enthalpy of formation of argon gas equal to zero?

  • ABecause argon gas has eight electrons in its valence shell
  • BBecause argon gas is a poor conductor of heat and electricity
  • CBecause argon gas is an inert gas
  • DBecause the standard enthalpy of formation of argon gas in its standard state is always zero

Q9:

Arrange the following compounds ascendingly according to their thermal stability.

The Compound BaCl()2sBaO()sBaCO()3sBaSO()4s
Δ𝐻(/)kJmol858.6548.11,2131,473.2
  • ABaSO()>BaCO()>BaO()>BaCl()432ssss
  • BBaSO()>BaCl()>BaO()>BaCO()423ssss
  • CBaO()>BaCl()>BaCO()>BaSO()ssss234
  • DBaSO()>BaCO()>BaCl()>BaO()432ssss

Q10:

What is the value of the standard enthalpy of formation of any element in its standard state?

This lesson includes 19 additional questions and 6 additional question variations for subscribers.

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