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Why look for black precipitate FeS in the bottom instead of on the surface during a test with H2S in aqueous solution?
Wiki User
∙ 14y ago
To detect hydrogen sulfide production, a heavy metal salt containing ferrous iron is added to a nutrient culture medium, when hydrogen sulfide is produced the sulfide reacts with the metal salt producing the black precipitate.
Wiki User
∙ 11y ago
Wiki User
∙ 12y agoThe FeS appears as a black precipitate in the butt (or bottom) of the test tube.
The iron, Fe combines with H2S to form FeS (ferrous sulfide) a black compound. This will turn the butt (or bottom) of test tube black. Thus, a black butt indicates an H2S production.
Wiki User
∙ 14y agoBecause black coloured FeS is heavier than water and can not float on the surface.
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What are the differences between colloidal precipitate and crystalline precipitate?
Crystalline precipitates have less surface area than the colloidal precipitates, therefore they are more pure. Additionally, crystalline precipitates, because they are larger, are more easily separated from the surrounding solution.
How do you test for iron II in an iron tablet?
Drop a solution of this in Sodium hydroxide solution, you will see a greenish precipitate instantly, this is the test for Iron(II) ions. Note that after sometime, the Greenish precipitate will turn to reddish.
Why phospholipids form a thin layer on the surface of aqueous solution?
Phospholipids have a hydrophilic head and two hydrophobic tails each. When phospholipids are exposed to water, they arrange themselves in a bi-layer sheet with the tails facing towards the center of the sheet, and away from the water.
What happens to zinc when dipped in silver nitrate?
Parts of the zinc near its interface with an aqueous solution of silver nitrate dissolve into zinc cations in the soution, and the corresponding electrical charge of silver cations is reduced to metallic silver, usually adhering to the surface of the remaining zinc.
What happens to zinc when dipped in tin acetate?
Parts of the zinc near its interface with an aqueous solution of tin acetate dissolve into zinc cations in the soution, and the corresponding electrical charge of tin cations is reduced to metallic tin, usually adhering to the surface of the remaining zinc.
What precipitate is formed when magnesium and silver nitrate mix?
Silver metal, the magnesium displaces the silver from solution. It's not really a "precipitate" exactly; the silver forms deposits on the surface of the magnesium instead of crystallizing in the solvent.
What are the differences between colloidal precipitate and crystalline precipitate?
Crystalline precipitates have less surface area than the colloidal precipitates, therefore they are more pure. Additionally, crystalline precipitates, because they are larger, are more easily separated from the surrounding solution.
What are the results got from the reaction of Al with KOH?
If the KOH is in a moderately concentrated aqueous solution, the net reaction can be: 2 Al + 6 H2O => 2 Al(OH)3 + 3 H2. In this instance, the KOH does not undergo any net reaction; instead it catalyzes the reaction between aluminum and water by preventing the solid aluminum from maintaining a passivation layer on its surface. If the KOH is in a still more concentrated aqueous solution, the reaction can be: 2 Al + 4 KOH => K2Al2O4 + H2.
What would happen to a saturated solution if cooled in the refrigerator?
If it is saturated with a solid solute, you would expect some of the solid to precipitate out - as long as the solid could find a surface to nucleate on. If it is saturated with a gas, you would expect more gas to dissolve into it as long as it was still in contact with the saturating gas in the gas phase.
Why look for black precipitate in the butt instead of on the surface of an H2S test?
The black precipitate usually sink to the bottom which the reaction took place in. The reaction takes place at the bottom because it only occurs under anaerobic conditions, and it does not sink to the bottom as it only occurs at the bottom, not around oxygen at the top of the tube.
Three factors that can manipulate a voltaic cell?
Concentration of aqueous solutions. Temperature of aqueous solutions. Electrode surface area.
Reacting copper II sulfate with iron yields?
If an aqueous solution of copper(II) sulfate is contacted with metallic iron, at the least the surface of the iron passes into solution and is replaced by a layer of metallic copper. This is an example of displacement by a metal higher in the electromotive series than the metal it displaces.
What will happen when a gram positive bacterium is placed in a aqueous solution of lysozyme and 10 percent sucrose?
The cell of Gram+ bacteria will break down against lysozyme and the cell will be injured but when it placed in sucrose the nutrient will be absorbed by the surface
How do you test for iron II in an iron tablet?
Drop a solution of this in Sodium hydroxide solution, you will see a greenish precipitate instantly, this is the test for Iron(II) ions. Note that after sometime, the Greenish precipitate will turn to reddish.
Why phospholipids form a thin layer on the surface of aqueous solution?
Phospholipids have a hydrophilic head and two hydrophobic tails each. When phospholipids are exposed to water, they arrange themselves in a bi-layer sheet with the tails facing towards the center of the sheet, and away from the water.
What happens to zinc when dipped in silver nitrate?
Parts of the zinc near its interface with an aqueous solution of silver nitrate dissolve into zinc cations in the soution, and the corresponding electrical charge of silver cations is reduced to metallic silver, usually adhering to the surface of the remaining zinc.
What happens to zinc when dipped in tin acetate?
Parts of the zinc near its interface with an aqueous solution of tin acetate dissolve into zinc cations in the soution, and the corresponding electrical charge of tin cations is reduced to metallic tin, usually adhering to the surface of the remaining zinc.
