inorganic chemistry Flashcards
does reactivity increase/decrease down group 2
increase due to increased electron shielding and atomic radius and electron further from nucleus
what does a metal and water make
metal hydroxide and hydrogen
how do the metals react differently with steam
Mg has a much faster reaction due to the extra energy so it burns in steam with a bright white flame
what do metals and chlorine produce
metal chloride (white ppt)
what do metals and oxygen make
metal oxides
more vigorous down group so barium and strontium may produce peroxides
what do metals and dilute acids make
hydrogen gas bubbles and metal compounds eg MgCl2
what do group 2 hydroxides and dilute acids make
a salt and water
what is the trend of group 2 hydroxide solubility
increases down group therefore MgOH2 used in medicine to neutralise acids
what is the trend of group 2 sulfate solubility
decreases down group therefore BaSO4 used as medical tracer to image internal organs as it cannot be absorbed into bloodstream
what can you use to test for sulfate ions
BaCl2 and HClp as it produces BaSO4 which is a white ppt
what does thermal decomposition of group 2 carbonates produce
metal oxide (white powder) and carbon dioxide
XCO3 -> XO + CO2
what does thermal decomposition of group 2 nitrates produce
metal oxide, nitrogen dioxide and oxygen
2X(NO3)2 -> 2XO + 4NO2 + O2
what does thermal decomposition of group 1 nitrates produce
lithium - same as group 2 (metal oxide, nitrogen dioxide and oxygen)
other metals - metal nitrite and oxygen (rarely goes to completion)
2XNO3 -> 2XNO2 + O2
why do down group 1 and 2 elements form more stable carbonates/nitrates?
-ionic radius increases for same overall charge so charge density decreases
-larger ions can polarise the carbonate/nitrate less
-less polarised, more heat is required to seperate the 2 ions as bond between carbonate/nitrate is not distorted so stronger
describe a flame test procedure
1) dip nichrome wire in conc HCl to clean it and then in a blue bunsen burner flame
2) repeat cleaning until no colour is produced in flame
3) dip wire into HCl then into unknown metal compound and place into flame, observe colour produced
what colour flame does lithium produce
red
what colour flame does sodium produce
yellow/orange
what colour flame does potassium produce
lilac
what colour flame does magnesium produce
no colour change
what colour flame does calcium produce
brick red
what colour flame does strontium produce
crimson red
what colour flame does barium produce
pale green
how do flame tests work
energy supplied from flame promotes electrons to orbitals with a higher energy
electrons drop back down to original orbital, releasing energy some of which is in the form of light
why does magnesium and other metals produce no colour change
the energy emitted has a wavelength which is not in the visible light part of electromagnetic spectrum
trend in electronegativity of group 7 elements
decreases down group due to atomic radius increasing therefore more shielding so less attraction of pair of electrons to the positive nucleus as it is further away so harder to attract a pair of electrons in a covalent bond
trend in melting point of group 7 elements
increases down group as halogens have more electrons so more London forces to overcome
trend in reactivity of halogens
decreases down group - atomic radius and shielding increases
trend in halogens oxidising agents
decreases down group
trend in halide ions reducing agents
increases down group
redox of H2SO4 by sodium Cl and F
NaF + H2SO4 -> NaHSO4 + HF
doesnt reduce - same for chlorine
produces misty fumes
redox of H2SO4 by sodium Br
NaBr + H2SO4 -> NaHSO4 + HBr (misty fumes)
2HBr + H2SO4 -> Br2 + SO2 + 2H2O (orange fumes of Br2 + choking fumes of SO2)
redox of H2SO4 by sodium I
NaI + H2SO4 -> NaHSO4 + HI
2HI + H2SO4 -> I2 + SO2 + 2H2O (solid iodine and choking fumes)
6HI + SO2 + -> H2S + 3I2 + 2H2O (toxic gas produces smelling of egg)
how does chlorine react with cold water
Cl2 + H2O -> ClO- + Cl- + 2H+
used in water treatment systems to use small portions of chlorine to kill bacteria
how does chlorine react with cold dilute alkali NaOH compared to hot concentrated
cold:
2NaOH + Cl2 -> NaClO + NaCl + H2O
used in bleach production
hot:
3Cl2 + 6NaOH -> NaClO3 + 5NaCl + 3H2O
how do the halogens react with acidifed silver nitrate (AgNO3)
Cl- white ppt
Br- cream ppt
I- yellow ppt
add dilute NH3
Cl- ppt dissolves
Br + I- no change
add conc NH3
Cl + Br- ppt dissolves
I- no change
what do hydrogen halides and ammonia gas form
ammonium salts in acid base reaction
HCl + NH3 -> NH4Cl
what do hydrogen halides and water form
dilute acids, the H+ ions in hydrogen halide dissociating to form hydroxonium ions with water
HCl +H2O -> Cl- + H3O+
how to test for carbonate/hydrogen carbonate ions
add any acid and it should fizz as CO2 gas is given off, bubble through limewater
XCO3 + 2HCl -> CO2 + H2O + XCl2
how to test for ammonium ions
add NaOH and ammonia gas will be produced which turns damp red litmus paper blue
