Oquizy

Hydrogen gas reacts with chlorine gas to form hydrogen chloride according to the following equation: H₂ + Cl₂ → 2HCl. The bond energies of the relevant bonds are:
- H–H = 436 kJ/mol
- Cl–Cl = 243 kJ/mol
- H–Cl = 431 kJ/mol.
What is the overall enthalpy change?

+179 kJ/mol +272 kJ/mol –183 kJ/mol –430 kJ/mol

Which statement correctly defines enthalpy change (ΔH)?

The change in energy of bonds only The energy needed to start a reaction The heat change at constant pressure The temperature change of the surroundings

What does arrow 1 represent?

Activation energy Bond energy of products Energy released Enthalpy change

Which statement is correct?

Bond breaking is endothermic Bond breaking is exothermic Bond making is endothermic Bond making requires energy

1.2g of Mg reacts with excess HCl, releasing 6000 J. Find ΔH in kJ/mol.

–12 –120 –30 –60

John mixes 30 cm³ HCl with 30 cm³ NaOH. The temperature change is 6.0 °C. What is total energy released?

1005 J 1505 J 2004 J 2510 J

Quiz: Chemistry - Chemical Energetics