C10

Balancing Overview
- Balancing is essential for ensuring that the number of atoms for each element is equal in the reactants and products of a chemical reaction.
Phosphorus Balancing
- Left side: 1 Phosphorus atom
- Right side: 1 Phosphorus atom
Chlorine Balancing
- Chlorine exists in one reactant (HCl) and one product; adjust the coefficient to match
- Placed a coefficient of 8 in front of HCl to balance chlorine.
Hydrogen and Oxygen Balancing
- Left Side: 8 Hydrogen atoms (from 4 HCl)
- Right Side: 8 Hydrogen atoms (3 from H2O + 5 from HCl)
- Left Side: 4 Oxygen atoms; Right Side: 4 Oxygen atoms (from 4 HCl)

Definition of Stoichiometry
- Stoichiometry refers to the calculation of reactants and products in chemical reactions
Limiting Reagent Identification
- Essential to identify the limiting reagent when amounts of reactants are given.
Example Calculation
- Calculate moles of phosphorus pentachloride (PCl5) provided:
- Given mass: 208.24 g
- Molar mass (PCl5) = 208.24 g/mol
- $ext{Moles of PCl5} = rac{208.24 ext{ g}}{208.24 ext{ g/mol}} = 1.5 ext{ moles}$
Water Requirement Calculation
- Each mole of PCl5 corresponds to 4 moles of water:
- $ext{Total Water Needed} = 1.5 ext{ mol PCl5} imes 4 ext{ mol H2O/mol PCl5} = 6 ext{ moles H2O}$
Actual Water Amount
- Calculate actual moles of available water from mass.

Limiting Reagent
- If the actual moles of water are less than the required amount, water is the limiting reagent.
Calculate Remaining PCl5
- Determine moles of PCl5 that actually reacted:
- Reacted Water: 1.5 mol H2O corresponds to 1 mole of PCl5:
- $1.5 ext{ mol H2O} imes rac{1 ext{ mol PCl5}}{4 ext{ mol H2O}} = 0.375 ext{ mol PCl5}$
- Remaining PCl5:
- $1.5 ext{ mol PCl5} - 0.375 ext{ mol PCl5} = 1.125 ext{ mol PCl5}$

Definitions
- Theoretical Yield: Maximum amount of product formed based on stoichiometry.
- Actual Yield: Mass of product obtained from experiment.
- Calculation of Percent Yield:
- $ext{Percent Yield} = rac{ ext{Actual Yield}}{ ext{Theoretical Yield}} imes 100 ext{ \%}$
Loss of Products
- There may be loss of products during transfer or measurement.

Neutralization Reaction Example
- Reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl).
- Theoretical yield is calculated from stoichiometry, but actual yield is usually less.

Energy
- Energy associated with changes in heat and work.
- Light absorption and emission relate to energy transfer in atoms:
- Absorbing light increases electron energy levels.
- Emitting light decreases electron energy levels, causing relaxation.
Heat and Work as Forms of Energy
- Heat: Energy transferred between systems due to temperature differences.
- Work: Force applied over a distance, defined as:
  $ext{Work} = ext{Force} imes ext{Distance}$
- For example, pushing an object:
  - 1 Newton applied over 1 meter results in:
    $ext{1 Joule} = ext{1 Newton} imes ext{1 meter}$
Types of Energy
- Kinetic Energy: Associated with motion.
- Potential Energy: Energy stored due to position.
- Gravitational Potential Energy: Increases with height.
- Elastic Potential Energy: Stored in stretched or compressed materials (like springs).
- Chemical Potential Energy: Energy stored in bonds of molecules.

Joule
- Base unit of energy defined as 1 Newton-meter:
  $1 ext{ Joule} = 1 ext{ Newton} imes 1 ext{ meter}$
Calorie
- Small calorie (with small 'c') is the energy needed to raise the temperature of 1 gram of water by 1 degree Celsius:
  $1 ext{ small calorie} = 4.184 ext{ Joules}$
- Large calorie (with capital 'C') is defined as:
  $1 ext{ large calorie} = 1,000 ext{ small calories}$
Conversions
- Conversions between calories and joules are essential in calculations involving energy.

Conservation of Energy
- Energy cannot be created or destroyed, only transformed or transferred.
- Importance in thermal chemistry and reaction energy analysis.