Lecture 1- Chemical Reactivity Flashcards
(32 cards)
Definition of work.
The distance moved against an apposing force.
Equation for work.
work= force x distance
What is the unit of measurement for work and energy?
Joules
What is 1 joule equal to?
The amount of energy required to move 1kg substance 10cm against gravity.
What is 1 calorie equal to?
The amount heat required to raise the temperature of exactly 1g of water by 1 degree Celsius.
What is 1 calorie equal to in joules?
4.184 Joules
What is potential energy?
Is stored energy and
energy of position
Equation for potential energy.
PE= mgh m= mass in kg g= acceleration due to gravity h= height in metres
What is kinetic energy?
Energy of motion. Depends on both mass and velocity.
Equation for kinetic energy
KE= 1/2 mv^2
m= mass in kg v= velocity in metres/second
What is the 1st law of thermodynamics?
Energy cannot be created or destroyed by any physical or chemical changes. Can only be converted from one form to another.
What does E=mc^2 mean?
If mass is destroyed, energy is created. If energy is destroyed mass is created.
Types of energy.
Potential energy. Kinetic energy. Electromagnetic energy. Nuclear. Chemical energy.
How do reactions occur?
They occur due to collision theory. Particles must c… but not all c.. cause r…
Must be fast enough
Correct orientation
What affects a chemical reaction?
Temperature, concentration and catalyst.
What is enthalpy change?
The change in energy (difference between bond energies of reactants and products).
It can be measured.
△H.
△H°= H products- H reactants
What is enthalpy?
The heat content of a substance at constant pressure. Is intternal energy.
This cannot be measured.
What is the standard state of an element.
The form in which the element exists under conditions of 1 atmosphere and 25°C (standard conditions).
What is the standard state of a compound?
Standard state of gaseous substance is pressure of 1 atmosphere.
The standard state for a pure solid or liquid is is the state it would be at 1 atmosphere.
For a substance in solution, the standard state is concentration of 1M.
What is exothermic?
Products contain less energy than reactants. Heat is released. e.g. burning, respiration. The temperature of system will rise. △H will be negative.
What is endothermic?
Products contain more energy than reactants. Heat taken in. e.g. photosynthesis Temperature of system will fall. △H is positive.
What is entropy?
Measures the amount of energetic disorder in a system.
Greater the disorder of randomness the greater the entropy.
S has units J per mole kelvin
△S= S final- S initial
△S total= △S system + △S surroundings
Law of entropy.
Entropy tends to a maximum.
All spontaneous changes overall an overall increase in entropy.
What is gibbs free energy?
Energy from a reaction free to do work.
