Other Conversions (Volume and Heat)

• Volume @ STP can be found using the conversion factor 22.4l/mol.
• Heat  can be included as a separate term in Chemical reactions [Enthalpy =chemical heat]
• Rxns that releases are Exothermic (A+B= C+ Energy)
• Rxns that absorbs heat are Endothermic ( A+B+Energy=C)
• Both reactions can be used in Stoichiometry.

Examples:

• When Zinc reacts with Hydrochloric Acid exactly 5.00L of Hydrogen gas is produced @ STP. What mass of Zinc was reacted?

Zn + 2HCl→ ZnCl₂ + H₂

5.00L H₂  x 1 mol/22.4 L x 1 mol/1mol x 6.4 g/ 1 mol =14.59821 →14.6 g

• In the formation of copper (II) oxide. 8.0g of Copper react. How many litres of Oxygen @ STP  are needed?

2 Cu +O₂ = 2CuO

8.0g Cu x 1 Cu/ 63.5 g Cu= 0.1259 mol cu

0.1259 mol Cu x 1 O₂/ 2 Cu= 0.06295 mol O₂

0.06295 mol O₂ x 22.4 L/ mol = 1.41 L