Module 2 Foundations in Chemistry Flashcards
State the location, charge and mass of a proton
Located in nucleus. Charge is +1, mass is 1
State the location, charge and mass of a neutron
Located in nucleus. Charge is 0, mass is 1
State the location, charge and mass of an electron
Located in electron shells. Charge is -1, mass is 1/1840
What does the atomic number show?
Number of protons in the nucleus of an atom
What does the mass number show?
Number of protons and neutrons in the nucleus of an atom
Define the term ‘isotope’
Atoms of the same element with the same number of protons (and electrons) but differing numbers of neutrons in the nucleus. Therefore isotopes of the same element have the same atomic number but different mass numbers.
Why do isotopes of the same element have the same chemical behaviour as one another?
They have the same electron configuration so will react the same as one another
Define the term ‘relative atomic mass’
The weighted mean mass of one atom of an element compared to 1/12 of the mass of an atom of carbon-12
Define the term ‘relative molecular mass’ and state when it should be used.
The weighted mean mass of one molecule compared to 1/12 of the mass of an atom of carbon-12. Used when referring to a covalent compound.
Define the term ‘relative formula mass’ and state when it should be used.
The weighted mean mass of one formula unit compared to 1/12 of the mass of an atom of carbon-12. Used when referring to an ionic compound.
Define the term ‘relative isotopic mass’
The mass of one atom of an isotope compared to 1/12 of the mass of an atom of carbon-12.
Define the term ‘strong acid’
A strong acid is a proton donor that fully dissociates into solution
Define the term ‘weak acid’
A weak acid is a proton donor that only partially dissociates into solution. Some hydrogen ions will remain attached to the acid molecule
Define the term ‘base’
A base is a proton accepter
Define the term ‘alkali’
A water soluble base
What is formed in the reaction between an acid and an alkali?
Salt and water
What is a salt?
A salt is the product of a reaction in which the hydrogen ions of the acid are replaced by metal or ammonium ions
Why is the mole used?
To measure the amount of substance without having to record a very large number of significant figures.
What is Avogadro’s number?
The number of atoms in 12.000g of carbon-12
What is the molar mass?
The mass, in grams, of one mole of a substance
What are the units of molar mass?
grams per mole (g mol-1)
How do you find a substance’s molar mass?
Look on the periodic table for its relative atomic/ molecular mass, then add correct units of grams per mol.
What is the calculation linking moles, mass and molar mass?
number of moles (mol)= mass (g) / molar mass (g/mol)
What is the calculation linking moles, number of particles and Avogadro’s constant?
number of moles (mol)= number of particles / Avogadro’s constant
One mole of any gaseous substance will occupy ______dm³ at room temperature and pressure
24
How do you convert between dm³ and cm³ ?
1000cm³ =1dm³
What is the equation linking gas volume and number of moles?
gas volume (dm³ )= moles (mol) x 24
Define ‘concentration’
Concentration is a measure of how many moles there are of a substance in a particular volume of an aqueous solution
What are the units of concentration?
mol dm⁻³
What is a monobasic acid?
An acid that donates 1 hydrogen ion per molecule of acid
How do you calculate the pH of a strong monobasic acid?
-log (concentration)= pH
What is a standard solution?
A solution of known concentration
Why are standard solutions used in chemistry?
By reacting other solutions of unknown concentration with the standard solution, we can work out the unknown concentration e.g. in titration
Describe how to weigh out an exact mass of solid during the preparation of a standard solution (weighing by difference).
- Using a spatula, weigh out approximately 2.5g of solid into a weighing boat.
- Record the exact mass of solid and weighing boat using a balance.
- Transfer the solid to a beaker, and wash the weighing boat with distilled water into the beaker to ensure that all the solid is dissolved
- Re-weigh and record the mass of the used weighing boat.
- You can now work out the exact mass of solid used by taking the mass of the boat away from the total mass of boat and solid.
Describe how to make a standard solution after finding the exact mass of solid used (weighed by difference)
- Transfer the solid into an 100cm³ beaker. Wash the weighing boat with distilled water into the beaker to ensure all of the solid is transferred
- Dissolve all of the solid in distilled water from a wash bottle. Stir with a glass stirring rod until all of the solid is dissolved.
- Transfer this solution into a 250cm³ volumetric flask through a funnel. Rinse the beaker and stirring rod with more distilled water and transfer the washings to the volumetric flask to ensure all of the solid is transferred.
- Add distilled water up until you have almost reached the 250cm³ graduation line. Then remove the funnel and add distilled water with a pipette until the bottom of the meniscus is touching the graduation line.
- Stopper the flask and gently invert a few times so that the concentration is the same throughout.
- Calculate the concentration of your solution using mass/Mr to find moles, then use moles/ volume to find concentration.
Define the term ‘ionic bond’
The electrostatic attraction between oppositely charged ions
How are ionic bonds formed?
When a metal transfers its valence electrons to a non-metal.
Define the term ‘covalent bond’.
The STRONG electrostatic attraction between a shared pair of electrons and the nuclei of the two bonded atoms
How are ionic compounds drawn?
Dot and cross diagrams with brackets showing the charge drawn around ions.
How are covalent compounds drawn?
Dot and cross diagrams with dots and crosses showing where electrons are shared.
Covalent molecules form when two ___-___ ____ electrons in covalent bonds.
non-metals, share
What are oxidation and reduction?
oxidation- loss of electrons
reduction- gain of electrons
What is an oxidation state?
a + or - number that tells us the number of electrons an element has donated or accepted during a chemical reaction.
When is the oxidation state of hydrogen NOT +1?
When hydrogen is bonded to a metal
When is the oxidation state of oxygen NOT 2-?
When oxygen is bonded to fluorine or is part of a peroxide
When do halogens have an oxidation state other than 1-?
When chlorine, bromine and iodine are bonded to oxygen