C4 - Predicting and identifying reactions and products Flashcards
What name do the Group 1 metals have?
Why do they have this name?
- Alkali metals
- They form alkaline solutions in water.
Group 1 metals properties compared to other metals (Similarities and comparisions)
Similarly:
- Shiny when freshly cut
- Good conductors of metals
However:
- Soft enough to cut with a knife
- More reactive than other metals
Trends shown by the Group 1 metals as you go down
- They become softer.
- Melting & boiling points decrease.
(delocalised electrons are closer to atomic nucleus, so electrostatic forces of attraction are greater) - Density generally increases (sodium is the exception).
- Reactivity increases.
(it is easier to loose valence shell electrons with more shells; further for nuclei, weaker forces of attraction)
Alkali metals and water reaction word equation
Alkali Metal + Water –> Metal Hydroxide + Hydrogen
How do the different alkali metals react with water?
- Lithium fizzes and slowly disappears
- Sodium melts to form a silvery ball, fizzes vigorously, and quickly disappears.
- Potassium quickly ignites, burns with a lilac flame, and very quickly disappears.
How do the different halogens exist at room temperature?
- Fluorine (Fl2) is a pale yellow gas.
- Chlorine (Cl2) is a green gas.
- Bromine (Br2) is an orange-brown liquid that vaporises easily.
- Iodine (I2) is a shiny grey-black crystalline solid that sublimes to form a purple vapour.
Trends shown by the Group 7 halogens
As you go down:
- Density increases.
- Melting points and boiling points increase.
(larger molecules, stronger IM forces)
- Reactivity decreases.
(easier to gain electrons when the valence shell is closer to the atomic nuclei; stronger electrostatic forces of attraction)
Why are the noble gases so unreactive?
They have full outer shells of electrons, so they have no tendency to lose/gain electrons.
Trends shown by the Group 8 Noble Gases
They are monoatomic.
As you go down:
- The attractive forces between atoms gets stronger.
- Their boiling point increases.
- Density increases.
Why do noble gases have low densities?
- Their atoms are far apart in the gas state.
- There is very little mass in a given volume.
Transition metals properties
- Shiny when freshly cut
- Good conductors of electricity
- Strong
- Malleable (they can be bent/hammered into shape)
Compared to the alkali metals, transitions metals are:
- Stronger and harder
- Have higher densities
- Have higher melting points (except for Mercury at liquid state)
- Less reactive (more useful for everyday activities)
Chemical properties of the transition metals
- Iron reacts slowly with water and oxygen to produce rust (hydrated iron (II) oxide)
- Gold, platinum, and iridium do not react with water or oxygen at all.
What colour ionic compounds of the different metals? (Transition vs Alkali)
- Alkali metals produced white or coloured ionic compounds.
- Transition metals produce coloured ionic compounds.
What charge do metal ions have? (Transition vs Alkali)
- Alkali metal ions have a single positive charge, as they lose one electron.
- Transition metals can form more than one type of ions.
Which metals are good catalysts?
Transition metals
How do metals react with water and dilute acids?
Water:
- Produces a metal hydroxide and hydrogen
- Calcium + Water –> Calcium Hydroxide + Hydrogen
Dilute acid:
- Produces a salt and hydrogen.
- Calcium + Hydrochloric acid –> Calcium Chloride + Hydrogen
Detecting carbon dioxide
- Limewater (calcium hydroxide solution)
- Bubble carbon dioxide through limewater and it will turn cloudy.
- This is because the calcium hydroxide reacts with carbon dioxide to form water and a white precipitate of calcium carbonate.
Detecting Chlorine
- Dampened piece of blue litmus paper.
- Hold it near the gas.
- It turns red then bleaches white.
Why does the litmus paper have to be dampened when testing for chlorine?
- Chlorine dissolves in the water to form an acidic solution which bleaches the litmus paper.
How to perform flame test
- Clean nichrome wire loop in hydrochloric acid, then distilled water.
- Put it over bunsen burner to ensure it’s clean.
- Dip clean loop into test powder/solution.
- Place under blue roaring flame.
Flame test results (Lithium, Sodium, Potassium, Calcium, Copper)
- Lithium: Red
- Sodium: Yellow
- Potassium: Lilac
- Calcium: Orange-red
- Copper: Green-blue
Hydroxide precipitate tests (Iron2, Iron3, Copper2, Calcium, Zinc)
- Iron(II): Green
- Iron(III): Orange-brown
- Copper(II): Blue
- Calcium: White
- Zinc: White
Add few drops sodium hydroxide solution to the solution containing the ions.
Detecting sulphate ions
- Add few drops of dilute hydrochloric acid
- Add few drops of barium chloride solution
- White precipitate SHOULD form.
Detecting carbonate ions
- Add few drops of dilute hydrochloric acid.
- Bubbles of gas should produce (carbon dioxide).
- Confirm this is CO2 but bubbling it through limewater.
Detecting halide ions
- Add few drops of dilute nitric acid
- Add few drops of silver nitrate solution
- Chloride: White
- Bromide: Cream
- Iodide: Yellow
Advantages of instrumental methods of analysis
- Sensitivity: They can analyse very small amounts of substances.
- Accuracy: They are very accurate and can be calibrated to a universally accepted standard.
- Speed: They run all the time and analyse quickly.
