Chem Practical
Terms
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- density
- ratio of mass per unit volume
- intensive property
- property that doesn\'t change when you take away some the sample
- mixture
- any material made up of 2 or more substances that are not chemically combined
- empirical formula
- the simplest whole no. ratio of atoms in a compound
- Law of Constant Composition
- any pure chemical compound that is made up of 2 or more elements in the same proportion by mass
- calorimeter
- container w/ insulated walls that prevents rapid heat exchange btwn the walls and its surroundings
- specific heat
- intensive physical property, is the quantity of heat in cal necessary to raise the temp of 1 g of substance by 1 C
- Law of Dulong & Petit
- atoms of all simple bodies have exactly the same capacity for heat, mass of water x specific heat of H2O x change in temp of water/ mass of the substance x change in temp of atoms = specific heat
- Conservation of Energy
- energy is being neither created nor distroyed, only changed from one form to another and the total amount of energy is constant in a closed system
- exothermic
- heat is released by the reaction -change in heat
- endothermic
- heat is absorbed by the reation +change in heat
- Charles Law
- when the pressure is held constant, the volume of a fixed mass of ideal gas is in direct proportion to the temp in Kelvin
- effective collision
- a molecule collision that results in a reaction
- activation energy
- minimum energy necessary for the reaction to happen
- catalyst
- substance that increases the rate of reaction w/o itself being used up in the process
- titration
- addad a base to an acid until all the acid is neutralized
- end point
- when a sudden change in the pH occurs, meaning titration is done
- back titration
- adding excess base to an acid and then adding acid until the excess base is neutralized, counting how much acid was added will tell how much base was neutralized by acid in the 1st reaction
- linear measurement
- SI Unit: meter use: meterstick
- mass
- SI Unit: kilogram metric use balance
- volume
- SI Unit: m^3 metric unit: liters
- heat
- SI Unit: joule metric unit: calorie
- rate of reaction
- mols/min
- How does temperature affect density?
- When a liquid or a gas is heated, the molecules move faster and move apart, reducing density. The opposite happens during cooling.
- Techinques used to separate a mixture:(5)
- sublimation, extraction, decantation, filtration, evaporation
- sublimation
- involves heating a solid until it passes directly from solid phase into gaseous phase
- extraction
- uses a solvent to selectively dissolve 1 or more components from a solid mixture
- decantation
- this separates a liquid from an insoluble solid sediment by carefully pouring the liquid from the solid w/o disturbing the solid
- filtration
- this separates a solid from a liquid through the use of a porous material like a filter
- evaporation
- process of heating a mixture in order to drive off a volatile liquid
- Rates of reaction are dependent on what 5 variables? How does their change affect the rate of reaction?
- 1)nature of reactants- some compunds are more reactive than others 2)concentration- in most reactions, the rate increases when the concentration of either or both reactants is increased 3)surface area- an increase in the surface area of a solid will increase the rate of reaction 4)temperature- increasing the temp makes the reactants more energetc every time the temp increases by 10 C, the reaction rate doubles 5) catalyst- any substance that increases the reaction rate w/o being used up
- formula for equilibrium constant
- K=[products] [reactants] where the [] indicate mols/L at equilibrium
- Calculate % recovery in an experiment:
- weight of recovered solids/weight of initial mixture
- Calculate: % error
- actual value-calculated value actual value
- empirical formula of an oxide:
- weight of metal/ g/mol: weight of oxygen/ g/mol
- Empirical formula of a hydrate:
- mols H2O/ moles of anhydrous salt= 1: ration of H2O
- calculate volume of water drawn into a flask (v/t=v/t)
- boilng point of water= T2 room temp= T1 volume of flask= V2, V2-V1= volume of water
- Difference btwn accuracy and percision:
- accuracy-how good your device is at getting a true measurement percision-how reproducible the measurement is