Inorganic Chapter 2: Group 2 & Group 7 Flashcards
What is group 2 called?
Alkaline Earth metals
What is trend in Atomic Radius down group 2?
It increases - no. of shells increases
What is the trend in first ionisation energy down group 2?
It decreases - electrons get further away from the nucleus - easier to remove
What is the trend in reactivity down group 2?
It increases - electrons are easier to remove due to distance from nucleus
What is the trend in melting points down group 2?
Generally decreases - Metal ions get bigger, nuclei get further away from the delocalised electrons, easier to break bonds
What ions do group 2 elements form?
2+ ions
What do group 2 elements produce when reacting with water?
A metal hydroxide & Hydrogen
E.g. Ca + 2H2O -> Ca(OH) + H2
What happens to the oxidation state of group 2 elements when they react?
They are oxidised from a state of 0 to +2
What are the two factors that decrease first ionisation energy down group 2?
Increased shielding
Increased atomic radius
What do solubility trends with group 2 elements depend on?
The compound anion (OH, SO4, etc)
What is the trend down group 2 of solubility with singly charged anions?
Increases
What is the trend down group 2 of solubility with doubly charged anions?
Decreases
How can you test for sulfate ions?
Add acidified barium chloride, see a white ppt on a positive result
What are group 2 elements used for?
Neutralising acidity - often in agriculture or antacids
Magnesium is used to extract Titanium
Calcium compounds used to remove SO2
‘Barium meals’ for X-rays
How is Magnesium used to extract titanium?
It reduces the Ti
TiCl4 + 2Mg -> Ti + 2MgCl
How are calcium compounds used to remove SO2?
Flue gas desulfurisation - Mix the compound (CaO or CaCO3) with water, then sprayed it onto the flue gases.
CaO + 2H2O + SO2 -> CaSO3 + 2H2O
CaCO3 + 2H2O + SO2 -> CaSO3 + 2H2O + CO2
What is a ‘Barium meal’ and how does it work?
People eat small amount of barium sulfate, which is opaque to X-rays, and will coat the tissue of the digestive tract, showing it on X-rays to diagnose issues.
What is Group 7 called?
The Halogens
What ions do group 7 form?
1- ions
What is the trend of boiling points down group 7?
They increase - increasing strength of VdW forces as size increases
What is the trend in electronegativity down group 7?
It decreases - larger atoms have less attracting power than smaller atoms
What happens when you add a halogen to a halide solution formed with a less reactive halogen?
The less reactive halogen will be displaced & a new halide will be formed
What is the general rule for halide displacement?
The halogen will displace a halide if it’s made from a halogen below it in the periodic table.
How can we use displacement reactions of halides?
To determine which halide is present in a solution
What are some uses of Halogens?
Bleach
Cleaning swimming pools
How do you make bleach?
Sodium Hydroxide & Chlorine
2NaOH + Cl2 -> NaClO + NaCl + H2O
How does chlorine kill bacteria in water?
It undergoes disproportionation, and the chlorate (I) ions that are formed kill bacteria.
Cl2 + H2O <-> 2H+ + Cl- + ClO-
What are some risks associated with chlorine water treatment?
Chlorine gas is toxic if you breathe it in
Organic compounds within water can form carcinogenic chlorinated hydrocarbons when reacting with chlorine
What is the trend of reducing power going down group 7?
It increases - electrons are further away from the nucleus & there is greater shielding effect.
What is the reaction of flouride or chloride with sulfuric acid?
Produces HF or HCl - reaction stops there
e.g. NaF + H2SO4 -> NaHSO4 + HF
What is the reaction of Bromide with sulfuric acid?
Produces HBr, which then produces sulfur dioxide, bromine, and water with the sulfuric acid
NaBr + H2SO4 -> NaHSO4 + HBr
HBr + H2SO4 -> Br2 + SO2 + H2O
What is the reaction of Iodide with sulfuric acid?
Produces HI, which will then reduce H2SO4 and then further reduces the produced SO2 to H2S.
(Equations same as Br)
6HI + SO2 -> H2S + 3I2 + 2H2O
What solution is used to test for halides?
Silver Nitrate - forms a different colour precipitate depending on the ion.
Next, add Ammonia to identify possibility of Chlorine.
What colour ppt does silver nitrate form with Flourine?
No ppt
What colour ppt does silver nitrate form with Chlorine?
White
What colour ppt does silver nitrate form with Bromine?
Cream
What colour ppt does silver nitrate form with Iodine?
Yellow
What is the result of adding ammonia after a silver nitrate test?
Chlorine will form a white ppt
Bromine will form a cream ppt
Iodine will form a yellow ppt
What tests can you use to identify group 2 ions?
Flame tests
NaOH tests
What colour ppt does Mg form with NaOH?
white ppt
What colour ppt does Ca form with NaOH?
Slight white ppt
What colour ppt does Sr form with NaOH?
Slight white ppt
What colour ppt does Ba form with NaOH?
None
What colour does Ca go in a flame test?
Brick red
What colour does Sr go in a flame test?
red
What colour does Ba go in a flame test?
Green
What is a good test for ammonium ions?
Red litmus paper & NaOH - add NaOH to an ammonium solution, it’ll form ammonia gas, which will turn the litmus paper blue due to being alkaline.
How do you test for hydroxides?
Use a pH indicator, an alkaline result will form if the solution has hydroxides
How can you test for carbonates?
Add dilute hydrochloric acid, the solution will begin to fizz. Bubble this gas through limewater, and if the limewater goes cloudy, the solution contained carbonate ions.
