Enthalpy Flashcards
What is an exothermic reaction and what charge does it have?
Where energy is released into surroundings. Negative charge
What is an endothermic reaction and what charge does it have?
Where energy is absorbed from surroundings into reaction. Positive charge
What are the standard conditions?
101kpa
298k
What is the equation for working out enthalpy change?
q=mc◇t
Define the enthalpy change of reaction
The enthalpy change that occurs during a chemical reaction under standard conditions in the stoichemtric ratios
Define the enthalpy change of combustion
The enthalpy change that occurs when 1 mol of a substance is completely burnt in oxygen under standard conditions
Define enthalpy change of formation
The enthalpy change that occurs when 1 mol of a compound is formed from its elements in theor standard states under standard conditions
Define the enthalpy change of neutralisation
Enthalpy change that occurs when 1 mol of water is formed from the reaction of an acid and a base under standard conditions
Define bond enthalpy
The mean energy needed to break 1 mol of a given bond in a gaseous molecule
How do you work out bond enthalpy of a reaction?
Bonds broken-bonds made
Reactants - products
Calculate enthalpy of reactions using formation and combustion data
Outline the experiment for the enthalpy change of solutions.
Add excess zinc powder to 50.0cm³ of 1.00moldm³ copper (2) sulfate to a polyester cup. Record initial temperature of solution. Stir. Record final temperature of solution
Outline the experiment for enthalpy change of combustion
Using a measuring cylinder add 150cm³ of water into a beaker and record intital temperature. Add methanol to spirit burner and weigh.
Heat beaker and stir. After 3 mins remove flame and record temperature. Re weigh spirit burner.
Why are some enthalpy values not accurate?
Heat may have been lost to surroundings or evaporation
