Key idea
From bonding to thermodynamics
A second pathway moving from bonding and molecular shape to counting matter, reading chemical equations, reasoning about gases and understanding the first tools of thermodynamics.
Mendeleev · Chemistry pathway · level 2
From bonding to thermodynamics
A second pathway moving from bonding and molecular shape to counting matter, reading chemical equations, reasoning about gases and understanding the first tools of thermodynamics.
By the end, you will be able to…
reason about polaritypredict molecular shapemove from moles to stoichiometric ratiosidentify a limiting reactantuse PV = nRTinterpret ΔH, ΔS and ΔG
01Bond polarity02Molecular shape03Molecular polarity04The mole: counting the invisible05Stoichiometry: reading an equation as a ratio06Limiting reactant07Ideal gas: understanding PV = nRT08Enthalpy: tracking energy exchange09Entropy and Gibbs energy: favorable does not mean fast
Mendeleev · Challenge
End-of-path challenge
Combine geometry, amount of substance and energy in one line of reasoning.
1. Why is CO₂ nonpolar overall despite polar C=O bonds?
Show the reasoned answer
Its linear geometry places two equivalent dipoles in opposite directions, so they cancel.
2. For 2 H₂ + O₂ → 2 H₂O, 6 mol H₂ react with 2 mol O₂. Which reactant limits?
Show the reasoned answer
2 mol O₂ require 4 mol H₂. O₂ is limiting; 2 mol H₂ remain and 4 mol H₂O can form.
3. A change has ΔH = −40 kJ·mol⁻¹ and ΔS = −100 J·mol⁻¹·K⁻¹ at 298 K. Estimate ΔG.
Show the reasoned answer
Convert ΔS: −0.100 kJ·mol⁻¹·K⁻¹. ΔG = −40 − 298×(−0.100) ≈ −10.2 kJ·mol⁻¹, thermodynamically favorable under these conditions.
Key idea
From bonding to thermodynamics
Guided example
From bonding to thermodynamics
A second pathway moving from bonding and molecular shape to counting matter, reading chemical equations, reasoning about gases and understanding the first tools of thermodynamics.
Put it into practice
From bonding to thermodynamics
Choose a concrete case linked to From bonding to thermodynamics. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.