Thermal Chemistry Problem Solving

This lecture focuses on multi-step problems in thermal chemistry, emphasizing the application of previously learned concepts to solve complex calculations. Two examples are provided: the partial decomposition of sodium hydrogen carbonate and the roasting of zinc sulfide ore. The lecture demonstrates the use of stoichiometry and Hess's Law to determine energy requirements. The session concludes with a brief mention of the next lecture on collision theory.

What is the primary focus of multi-step problems in thermal chemistry?

• Introducing new theoretical concepts

• Applying previously learned concepts to complex calculations

• Memorizing chemical equations

• Focusing solely on qualitative analysis

In the decomposition of sodium hydrogen carbonate, what is the molar enthalpy change for decomposing one mole?

• 129.2 kJ

• 258.4 kJ

• 32.3 kJ

• 64.6 kJ

What is the first step in solving the sodium hydrogen carbonate decomposition problem?

• Calculating the total enthalpy change

• Determining the molar enthalpy change

• Converting mass to volume

• Applying Hess's Law

How many moles of sodium hydrogen carbonate are present in 100 kg of the substance?

• 2000 moles

• 500 moles

• 1000 moles

• 1190 moles

What is the total enthalpy required to partially decompose 100 kg of sodium hydrogen carbonate?

• 7.69 x 10^4 kJ

• 6.79 x 10^4 kJ

• 5.69 x 10^4 kJ

• 8.69 x 10^4 kJ

What is the target equation in the roasting process of zinc sulfide ore?

• The decomposition of sodium hydrogen carbonate

• The combustion of zinc

• The synthesis of zinc oxide

• The roasting process of zinc sulfide

Which law is employed to solve the enthalpy in the zinc sulfide roasting problem?

• Avogadro's Law

• Charles's Law

• Hess's Law

• Boyle's Law

How many moles of zinc sulfide are present in 50 kg of the ore?

• 700 moles

• 400 moles

• 600 moles

• 512.925 moles

What is the total enthalpy change when roasting 50 kg of zinc sulfide ore?

• -2.26 x 10^5 kJ

• -1.26 x 10^5 kJ

• -4.26 x 10^5 kJ

• -3.26 x 10^5 kJ

What is the best practice for mastering multi-step problems in thermal chemistry?

• Memorizing all chemical equations

• Ignoring stoichiometry

• Practicing a variety of problems

• Focusing only on theoretical concepts