The periodic table, chemistry calculations, salts test Flashcards
why could there be an apparent increase in mass?
gases in the air that would be not able to be weighed might be used in the reaction
why could there be an apparaent decrease in mass?
gases produced by the reaction would be diffused into the air, therefore could not be weighed.
what is the the law of conservation of mass?
- no atoms are lost or made during a chemical reaction so the mass of the products equals to the mass of the reactants
How do you calculate the RFM of a sbustance
relative atomic mass of all atoms added together
how do you caculate the %mass of an element in a compound?
mass of element in compound/ RFM of compound x 100
How do you calculate uncertainty?
range of results/ 2
or
result + or - resolution/ 2
What are chemical amounts measured in?
moles (symbol = mol)
how much is one mol of a substance?
same number as RFM of the substance but in grams. (eg. 1 mol of oxygen = 16 g)
how much is one mole of any substance compared to another?
the same amount of particles, atoms, ions, etc.
What is the value of the avogrado constant?
6.02 x 10^23 per mole
how do you calculate the number of moles?
moles = mass/ RFM
Reacting mass calculations
balancing number
known/ unknown mass
RFM
mass (RFM x balancing number)
statement of what is happening
divide to find mass produced from 1g
multiply by mass of reactant
How do you balance equations using reacting masses?
unbalanced symbol equation
masses that reacted in g from question
RFM
Moles (mass/ RFM)
divide by smallest ratio
balanced equation
How do you calculate concentration? (g/dm^3)
amount of substance (g) / volume of solution (dm^3)
what are the three most common acids?
- hydrochloric acid (HCl)
- Sulfuric acid (H2SO4)
- nitric acid (HNO3)
Types of salt that can form from the acids
- nitrate
- cholide
- sulfate
What can salts be used for?
- seasoning food
- dissolved in drinking water
- perserve food
- fertilizers (sulfate and nitrate salts)
What kind of reaction is the reaction between acids and metals?
- redox reaction
- (oxidation and reduction reaction taking place at the same time)
What is oxidation?
- gain of oxygen or losing of electrons of a substance in a reacton
What is reduction?
- losing of oxygen, gaining of electrons or gaining hydrogen by a substance in a reaction
what do all acids have?
hydrogen ions
What is the difference between an alkali and a base?
- alkalis are soluble, they can dissolve in water
- all alkalis are bases but not all bases are alkali
How do you identify a base?
- name ends with carbonate or oxide
How do you identify an alkali?
- if the metal is in group 1/2 ending with hydroxide
How do you identify a salt?
- ends with sulfate/ nitrate/ chloride
compound ions names
- hydroxide (OH-)
- nitrate ion (NO3-)
- sulfate ion (SO4 2-)
- carbonate ion (CO3 2-)
What is neutralisation?
When acids are neutralised by alkalis and bases to produce salt and water, and by metal carbonates to produce salts, water and carbon dioxide
What does alkalis and bases produce when they neutralise acids?
Water and salt
What do metal carbonates produce when they react with acid?
Salt, water, and carbon dioxide
What salt does the three most common acids make
Hydrochloric acid - chloride
Sulfuric acid - sulfate
Nitric acid - nitrite
How do you make pure, dry samples of soluble salts?
- measure aicd using measuring cylinder and pour it into beaker
- gently heat thte acid by placing it on a bunsen burner and a tripod (speeds up reaction)
- take acid off bunsen and add spatulas of the alkali/ base until the powder at the bottom of the beaker. (to make sure that the alkali/ base is in excess) the solution should turn into a different colour (blue for copper sulfate)
- remove the excess copper oxide by filtering it using a funnel and filitering paper (to get pure crystals of salt)
- pour the solution into evaporating basin and heat over a beaker of boiling water(if the solution is heated directly the crystals will break down)
- take evaporating basin off the water bath once half of the solution is gone and leave it out at room temp to let it evaporate naturally (larger crystals can form)
- after water has evaporated entirely, put crystals on filiter paper (to make sure that it is completely dry)
Why do we not use an oven to dry out the crystals?
- the cyrstals would turn into powder
- removes the water molecules from the crystal (needs water to remain crystal)
describe the colour of universal indicator from acid to alkali
acid - red, orange, yellow
neutral - green
alkali - blue, purple
what are strong acids in an aqueous solution?
completely ionised
what are weak acids in an aqueous solution?
partially ionised
how much does the concentration of hydrogen ions need to be diluted by to increase the pH by 1?
10 times, the less hydrogen ions, the higher the pH
What were early attempts to classify elements like?
- arranged in order of atomic weights
- incomplete (many elements unknown)
- some elements were placed in groups with elements that were not similar to them
How did Dmitri Mendeleev classify elements?
- left gaps in the periodic table
- in order of increasing atomic weights
- took into account properties of elements
- elements with similar properties lined up in groups
- 1869
this was before the discovery of protons, neutrons and electrons
How did Johann Wolfgang Dobereiner classify elements?
- law of triads
- placed elements in groups of 3
- 1817
How did John Newlands classify elements?
- law of octaves
- eight element together
- 1864
Who discovered neutrons?
James Chadwick
properties of metals
- form positive ions
- left hand side of periodic table
- good conductivity
- shiny surface
- high melting and boiling points
- solid at room temp
- malleable
- basic oxide
properties of non metals
- do not from positive ions (except hydrogen)
- right hand side
- poor conductivity (except for graphite)
- dull
- low melting and boiling points
- gases & other states at room temp
- brittle
- acidic oxide
