HL Chemistry - Topic 1: Stoichiometric Relationships Flashcards
What is an element?
Elements are substances made from one kind of atom
What is a compound?
Compounds are made from 2 or more elements CHEMICALLY COMBINED
What is a mixture?
Elements and compounds are interspersed with each other, but NOT chemically combined
What is a homogeneous mixture?
It has uniform composition and properties throughout
What is a heterogeneous mixture?
It has non-uniform composition, so its properties are not the same throughout
Is heterogeneous mixture or homogeneous mixture possible to be separated?
Heterogeneous mixture
Is air a homogeneous or heterogeneous mixture?
Homogeneous mixture
Is bronze (Alloy) a homogeneous or heterogeneous mixture?
Homogeneous mixture
Is concrete a homogeneous or heterogeneous mixture?
Heterogeneous mixture
Is orange juice with pulp a homogeneous or heterogeneous mixture?
Heterogeneous mixture
What technique can be used to separate the components of air. And, what is the property that is different in the components?
Fractional distillation (of liquid air). Boiling points
What technique can be used to separate the components of salt and sand. And, what is the property that is different in the components?
Solution and filtration. Solubility in water
What technique can be used to separate the components of pigments in food colours. And, what is the property that is different in the components?
Paper chromatography. Adsorption on cellulose
What technique can be used to separate the components of Sulfur and iron. And, what is the property that is different in the components?
Using a magnet. Magnetism
What is the definition of the relative atomic mass (Ar) of an element?
It is the weighted average mass of one atom compared to one twelfth the mass of a carbon-12 atom
What is the definition of the relative isotopic mass?
It is the mass of a particular atom of an isotope compared to one twelfth the mass of a carbon-12 atom
What is the definition of an isotope?
Atoms of the same element with a different number of neutrons
How is the relative atomic mass calculated?
The sum of (isotope PERCENTAGE abundance x relative isotopic mass) / 100
What is the definition of the relative molecular mass (Mr)?
It is the weighted average mass of a molecule compared to one twelfth the mass of a carbon-12 atom
What is the definition of molecular formula?
It is the formula that shows the number and type of each atom in a molecule
What is the definition of empirical formula?
It is the simplest whole number ratio of the atoms of each element present in one molecule
How to calculate empirical formula? Given mass and Mr
- Find the number of moles for each element
- Divide the moles with the lowest moles from all elements to give the ratio
How to calculate empirical formula? Given percentage composition by mass of its elements
- Divide the % by atomic masses to find the moles of each element
- Divide the moles with the lowest moles from all elements to give the ratio
How to calculate the molecular formula given the empirical formula and the molecular mass of the compound?
- Calculate the relative mass of empirical formula
- Divide molecular mass of compound by molecular mass of empirical formula
- Multiply the empirical formula from the answer in step 2
