Group 2 metals Flashcards
(30 cards)
What is the trend in atomic radius in group 2?
Increases
• due to the number of delocalised electrons(2)
• charge
• more shielding
• weaker attraction between nucleus and electron
What is the trend in 1st ionisation energy?
Decreases
• due to number of electrons
• charge
• more shielding
• weaker attraction to nucleus and outer electrons
What is the the trend in melting point in group 2?
Decreases
• size of ion increases
• weaker electrostatic attraction between positive ions and delocalised electrons
What happens when a group 2 metal reacts with water?
atom loses an electron becomes a 2+ ion
What is the equation for a metal (Mg) with water?
Mg(s) + 2H2O(l) > Mg(OH)2 + H2
What happens to reactivity down the group?
they become more reactive and reactions become more vigarous
What is the equation for Magnesium reacting with steam?
Mg(s) + H2O(g) > MgO(s) + H2(s)
What is the observation in a raction with magnesium and steam?
white flame and white solid
bright sparks
What is the trend in Hydroxides Solubility in water?
Solubility increases down the group
Why does pH of hydroxides increase down a group?
there are more hydroxide ions in the solution. this makes the solution more alkaline
What is the formula of a hydroxide metal (Ca)
Ca(OH)2
What is the test for magnesium ions?
add sodium hydroxide Na(OH)2 (or any soluble metal hydroxide)
if magnesium ions are present they will form a white precipitate of Mg(OH)2
What is the test for hydroxide ions?
Add magnesium chloride (or any soluble magnesium salt)
if hydroxide ions are present white precipitate of Mg(OH) 2 forms
What is the formula for a metal sulfate? (Sr)
SrSO4
What is the trend in solubility for metal sulfates?
Solubility decreases down a group
What is the test for barium ions?
add sodium sulfate or sulphuric acid
if barium ions are present white ppt of BaSO4 is formed because barium is insoluble
What is the test for sulfate ions?
add acidified barium chloride (or any barium salt)
if sulfate ions are present a white precipitate of BaSO4 forms
Why must the solution be acidified with HCL/HNO3 before testing for sulfate ions?
this removes carbonate ions that would interfere with the reaction
they form a ppt of BaCO3
How do you remove a precipitate using filtration?
• filter using gravity or a vacuum filtration
• wash to remove soluble impurities
• dry to remove water
What is the use of the compound Mg?
Used in the extraction of titanium from its ore?
What is the use of the compound Mg(OH)2?
Neutralises excess stomach acid (HCL)
What is the use of the compound Ca(OH)2?
Neutralises acidic soils
What is the use of the compound CaO & CaCO3?
CaO - flue gas desulfurisation
CaCO - neutralises SO2
What is the use of the compound BaSO4?
CT scans and X-rays
Also used in barium meals
safe to use as BaSO4 is insoluble and wont be absorbed
