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18 Cards in this Set
- Front
- Back
- 3rd side (hint)
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State and explain the trend in atomic radius of the elements Mg to Ba |
- atomic radius increases down group - more electron shells - meaning more shielding and less attraction between nucleus and outer shell - so atoms are bigger |
FEEL |
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State and explain the trend in first ionization energy of Elements Mg to Ba |
- first ionization energy decreases down the group - atoms have more shells and larger radius - resulting in more shielding too - therefore attraction between nucleus and outer electron is weaker and requires less energy to remove |
FEEL |
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State and explain the trend in melting point of elements Mg to Ba |
- Melting point decreases down the group - metal ions get bigger - so electrostatic attraction between positive metal ions and free electrons is weaker - so less energy required to overcome the force of attraction between them |
FEEL |
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State and explain the trend in reactivity of elements Mg to Ba |
- reactivity increases down the group - atoms get more shells and thus get bigger - attracting between outer electrons gets decreased - power electrons are now easier too remove |
FEEL |
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State solubility of group 2 metal hydroxides down the group |
It increases They become more soluble down the group So Mg(OH)2 has a very low solubility in water And Ba(OH)2 is relatively soluble in water |
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What’s alkalinity |
The measure of the capacity of something to rid H+ ions (to resist acidification) |
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How to test for Magnesium |
Use pair of tongues and place in open Bunsen burner flame Mg will combust in a bright white light |
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Test for magnesium through water |
Magnesium reacts with water to form Mg(OH)2 + H2 (gas) The hydrogen gas can be tested through a squeaky pop test If there is no precipitation then mg was present |
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Test for calcium through water |
Put calcium oxide (which can be obtained through combustion of Mg - eg in open Bunsen burner flame) into water It will form some Ca(OH)2 (aq) but as this is only slightly soluble in water, the solution will quickly become saturated As we continue to form Ca(OH)2 it no longer dissolves and instead forms a solid This is a white precipitate |
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What does the trend in solubility of group 2 hydroxides show us and how |
The alkalinity of the group 2 hydroxides - when hydroxides dissolve they release two OH- ions - these make solutions alkaline - the larger the concentration of these ions determine the alkalinity of the solution
High conc = higher pH Low conc = lover pH |
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What does the trend in solubility of group 2 hydroxides show us and how |
The alkalinity of the group 2 hydroxides - when hydroxides dissolve they release two OH- ions - these make solutions alkaline - the larger the concentration of these ions determine the alkalinity of the solution
High conc = higher pH Low conc = lover pH |
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What’s the approximate pH of barium hydroxide and magnesium hydroxide |
Ba(OH)2 - pH~13 Mg(OH)2 - pH~10 |
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Use of Mg(OH)2 in real life |
In Medicine - neutralizes excess stomach acid - treats constipation in the short term - is a weak alkali so wrong Han or damage stomach tissue |
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Use of Ca(OH)2 in real life |
In Agriculture - neutralizes acidic soils and makes them favorable for crop growth - regulated pH if soil (as it acts as a base) - but not too alkali as to kill or damage crops/wildlife/soil |
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State trend in solubility in group 2 metal sulphates down the group |
The opposite of with hydroxides Decreases down the group MgSO4 is very soluble in water BaSO4 completely insoluble in water! |
Think of BaSO4 |
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Use of BaSO4 in medicine |
Barium sulphate is given to patients right before an X-ray of their digestive system (AKA “Barium Meal”) - Barium strongly absorbs x rays allowing a clear visualization of digestive system - since barium sulphate is insoluble, it’s doesn’t enter the bloodstream |
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Use of BaSO4 to test for sulphates / sulphate ions |
- Get BaCl2 (soluble in water) - dissolve it in water and it’ll split into Ba+2 and Cl- ions - if SO4-2 ions are present, it’ll react with the Ba+2 ions and form BaSO4 - form insoluble white precipitate and this can be identified (and removed if needed) |
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Why do we add HCl or HNO3 to BaCl2 solution before we test for sulphates |
- If carbonate ions are present they’ll react with Ba+2 ions and form a white precipitate which can be a false positive test - HCl or HNO3 reacts with the carbonate ions (CO3-2) to from CO2 gas which escapes and prevents the false positive test |
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