2) Inorganic Chemistry Flashcards
Group 1 metals
Alkali metals - form alkaline solutions when they react with water
-lithium, sodium, potassium, rubidium, caesium, francium
-first column of periodic table
-share similar characteristic chemical properties - all have one electron in outermost shell
-compounds are all ionic
Group 1 properties
-soft metals
-low density
-low melting point
-very reactive - only need to lose one electron to become stable
Group 1 metals - reactive
-react quickly with oxygen –> oxides
-react with water
-NO TOUCHING - enough sweat on skin to give reaction - produces heat and very corrosive
-stored under oil
-Rb + Cs are too reactive - stored in sealed glass tube so no oxygen
Group 1 metals - reaction with water
metal + water –> metal hydroxide + hydrogen
2M + 2H20 –> 2MOH + H2
-form alkalis in water
Lithium + water
-relatively slow reaction
-doesn’t melt
-fizzing seen, heard
–> lithium hydroxide + hydrogen
Sodium + water
-large amounts of heat released, causes sodium to melt
-hydrogen released catches fire, causes ball of sodium to dash across the surface
–> sodium hydroxide + hydrogen
Potassium + water
-reacts more violently than Na
-enough heat released so hydrogen burns with lilac coloured flame
-melts into a shiny ball that dashes around the surface
Group 1 metals - reaction with oxygen
-form metal oxides
-alkali metals tarnish when exposed to air, dull coating
Group 1 metals - Physical trends
As you go down the group
-mp/ bp decreases
-density increases
-reactivity increases
Group 1 metals - reactivity in terms of electrons
-as atoms get bigger the outer electron is further from the nucleus - weaker forces of attraction between them
-less strongly attracted by the nucleus
-less energy required to overcome force of attraction
-lost more easily
Group 1 metals - halogens
-react with halogens to form compounds
-MX (LiCl, KBr)
Group 7 metals
-fluorine, chlorine, bromine, iodine, astatine
-similar reactions - all have 7 outer shell electrons
-non-metallic elements that are poisonous
-diatomic molecules - F2, Cl2
-react with metals and non metals to form compounds
Group 7 metals - physical properties
As you go down the group
-mp/ bp increases - as relative molecular mass increases - intermolecular forces increases
-colour increases
-reactivity decreases
Fluorine - appearance (room temp), characteristics, colour in solution
-yellow gas
-very reactive, poisonous
Chlorine - appearance (room temp), characteristics, colour in solution
-pale yellow-green gas
-reactive, poisonous, dense
-pale green
Bromine - appearance (room temp), characteristics, colour in solution
-red brown liquid
-dense red-brown volatile liquid
-orange
Iodine - appearance (room temp), characteristics, colour in solution
-purple-black solid
-shimmery, crystalline solid, sublimes to form a purple vapour
-dark brown
Halogen + non metal
-form simple molecular covalent structures
-e.g. halogen + hydrogen –> hydrogen halides
-fluorine is the most reactive (reacts with hydrogen at low temperatures in absence of light)
Halogen displacement reactions
-more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide
Chlorine, bromine, iodine - displacement reaction
Chlorine > bromine > iodine
Potassium bromide + chlorine
-chlorine displaces bromide ions
-yellow - orange colour of bromine seen
Potassium iodide + chlorine
-chlorine displaces iodide ions
-brown colour of iodine seen
Potassium iodide + bromine
-bromine displaces iodide ions
-brown colour of iodine is seen
Group 7 metals - reactivity in terms of electrons
-decreases
-if a shell is closer to the nucleus, it is more attracted to the nucleus - stronger tendency to form a 1- ion
-moving down the group, forces of attraction between the nucleus and outermost shell decreases
-harder for atoms to gain electrons
Composition of air
Oxygen - 21%
Nitrogen - 78%
Argon - 0.9%
Carbon dioxide - 0.04
Finding percentage of oxygen - using metals
1.Place wet iron filings inside the end of a burette
2. Using a clamp, stand the burette vertically over a trough of water.
3. Record the starting height of the water in the burette.
4. Leave for a few weeks then record the final height of the water in the burette.
5. Calculate the change in height of the water in the burette. This is the volume of oxygen that was originally in the burette.
6. To calculate the percentage by volume of oxygen in air, divide the change in the burette reading by the original volume of air in the burette and multiply by 100
-water level will rise as iron filings react with oxygen in the burette. Water rises to replace oxygen that has reacted
Finding percentage of oxygen - using non metals
- Place phosphorus on an evaporating dish, float dish in trough of water
- Ignite phosphorus, place bell jar into trough, cover dish
- Record starting height of water level in the bell jar
- Leave apparatus until phosphurus is extinguished
- Measure final water level
- Final - initial = volume of oxygen originally in the jar
- (Change in water level/ original volume) x 100
-combustion of phosphorus uses up oxygen, water rises to replace volume of oxygen used up
Combustion
-burning
-reactions involve a chemical change in which oxygen reacts with elements or compounds to produce oxides
-gives out heat - exothermic
Combustion reaction - magnesium
2Mg + O2 –> 2MgO
-intense white flame
-white powder produced (magnesium oxide)
Combustion - Sulfur reaction
S + O2 –> SO2
-blue flame
-colourless
-poisonous gas produced
Thermal decomposition
-reactions where a substance breaks down due to the action of heat
-one such reaction - thermal decomposition of metal carbonates
Thermal decomposition of metal carbonates
-carbonates of metals from the lower half of the reactivity series tend to decompose on heating
-metal carbonate –> metal oxide + carbon dioxide
-e.g copper (II) carbonate occurs readily on heating
-Copper(II) carbonate - green powder
-slowly darkens as black copper(II) oxide is produced
-CuCO3 –> CuO + CO2
The greenhouse effect
-When shortwave radiation from the sun strikes the Earth’s surface it is absorbed and re-emitted from the surface of the Earth as infrared radiation
-Much of the radiation is trapped inside the Earth’s atmosphere by greenhouse gases which can absorb and store the energy
-Carbon dioxide, methane and water vapour are gases that have this effect
Carbon dioxide - greenhouse effect
-traps extra heat
-enhanced greenhouse effect
-sources: burning wood, fossil fuels, respiration
Reactivity series
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-Potassium
-Sodium
-Lithium
-Calcium
-Magnesium
-Aluminum
-Carbon
-Zinc
-Iron
-Tin
-Lead
-Hydrogen
-Copper
-Silver
-Gold
Reactivity series - + water
metal + water –> metal hydroxide + hydrogen
-potassium: reacts violently
-Sodium: reacts quickly
-Calcium: reacts less quickly
-Mg, Fe, Zn + cold water - slow
Reactivity series - + dilute sulfuric/ hydrochloric acids
-only metals ABOVE hydrogen will react with dilute acids
-more reactive the metal, more vigorous the reaction will be
metal + acid –> salt + hydrogen
Reactivity series - metal displacement reactions (zinc + copper oxide)
-more reactive metal will displace a less reactive metal from its compounds
e.g. zinc + copper oxide –> zinc oxide + copper