chapter 8 reactivity trends Flashcards
what is the name for group 2 elements?
alkaline earth metals
what type of agents are group 2 metals?
reducing agents, this is because they have two outer shell electrons which they can lose allowing other atoms to receive them
what do group 2 elements form when they react with oxygen?
metal oxides
what do group 2 elements form when they react with water?
metal hydroxides and hydrogen
what effect does going down the group have on reactivity?
reactivity increases
why does the reactivity increase down the group?
•to form 2+ ions you require two ionisation energies
•I.Es decrease down the group because attraction between the nucleus and outer shell decreases due to increasing atomic radius and shielding.
what is reaction between group 2 oxides and water?
MO(s) + H2O(l) ~> M(OH)2(s)
describe the solubility of group 2 hydroxides in water.
solubility of hydroxides increases down the group so the resulting solutions contain for OH- ions and are more alkaline
compare the solubility of Mg(OH)2 and Ba(OH)2 in water.
•Mg(OH)2 is only slightly soluble so the solution has a low OH- conc and a pH of ~10
•Ba(OH)2 is much more soluble so the solution has a high OH- conc and a pH of ~13
describe an experiment to show the trend in solubility of group 2 hydroxides in water.
•add a spatula of each group 2 oxide to water in a test tube
•shake the mixture. there is insufficient water to dissolve all of the metal hydroxide that forms. you will have a saturated solution of each metal hydroxide with some white solid undissolved at the bottom of each test tube
•measure the pH of each solution. alkalinity will increase down the group
what are some uses of group 2 compounds as bases?
•Ca(OH)2 is used to neutralise the pH of acidic soils
•CaCO3 and Mg(OH)2 are used as antacids for increasing the pH of your stomach acid
what is the most reactive non metal group?
the halogens (group17)
in nature, how do halogens occur?
as stable halide ions dissolved in sea water or combined with Na or K as solid deposits
describe the trend in boiling point of halogens at room temp and pressure (RTP).
all halogens exist as diatomic molecules at RTP with boiling point increasing down the group
describe the appearance and state of halogens at RTP.
•F2 is a pale yellow gas
•Cl2 is a pale green gas
•Br2 is a red brown liquid
•I2 is a shiny grey black solid
what is the most common type of reaction of the halogens?
redox
what type of agents are halogens and why?
oxidising agents because they have oxidised another species
does reactivity increase or decrease down group 17?
decreases because it becomes harder to gain e-.
•atomic radius and shielding increases down the group
what are the colours of each halogen in water and cyclohexane?
•Cl2 is pale green/colourless in both
•Br2 is orange in both
•I2 is brown in water and violet in cyclohexane
describe the halogen displacement reactions.
•Cl2 reacts with Br- and I-
•Br2 reacts with I-
•I2 doesn’t react as it cannot displace
write the half equation for chlorine displacing bromide ions.
Cl2(aq) + 2Br-(aq) ~> 2Cl-(aq) + Br2(aq)
predict the properties of fluorine and astatine.
•Fl2 is a pale yellow gas reacting with almost every substance it comes into contact with
•At2 is extremely rare due to it decaying quickly so it has never been seen but is predicted to be the least reactive halogen
what is disproportionation?
redox reaction in which same element is being oxidised and reduced.
e.g Cl2 with water and cold dilute NaOH
what is the equation of chlorine with water?
Cl2(aq) + H2O(aq) ~> HClO(aq) + HCl(aq)
