5.11 to 5.16 Flashcards
accurate
how close a measurement is to true or accepted value of the quantity being measured
precise
reproducibility of a result or measurement
bias
the difference between the average of measurements made on the same object and its true value
random error
due to unpredictable or unknown fluctuations in variables that might affect experimental results
systematic error
skews the results to one side
random errors in titrations
- judging when the bottom of the meniscus is level with the graduation on a pipette
- judging the colour change at the end point
- taking a reading from the burette scale
systematic errors in titrations
when the results differ from the true value by the same amount each time
Limiting reagent
is a substance that is present in an amount that limits the the theoretical yield
theoretical yield
the mass of the product obtained if the reaction goes according to the equation
actual yield
the actual mass of the product obtained from a reaction
give three reasons why yields are not 100 %
- the reactants may not be totally pure
- there may be side reactions in which the reactants form different products
- some of the reactants may not react because the reaction is slow or because it comes to equilibrium
percentage yield equation
actual yield / predicted yield x100
high percentage yield
- reduces the reactants used
- reduces cost
atom economy
a measure of how efficiently a chemical reaction coverts the atoms in its reactant to atoms in the products
High atom economy
- reduces the production of unwanted by products
- makes the process more sustainable
