paper4 Flashcards
Describe the group 1 physical & chemical properties:
1️⃣shiny when freshly cut
1️⃣solid state at RT
1️⃣soft
1️⃣ conducts of electricity
What is the trend of group 1 metals going down the group?
1️⃣ density increases
1️⃣ melting point decreases
1️⃣ reactivity increases (fizzes —> flames)
Why do group 1 elements get more reactive down the group?
Want to loose 1 electron
Larger Atomic radius = weaker force of attraction
Shielding (more electron shells in way) = weaker force
What do group 1 metals produce when they react with water?
Hydrogen and an alkali (metal hydroxide)
What are some chemical and physical properties of group 7 elements?
7️⃣brittle
7️⃣poor conductors
7️⃣DIATOMIC
How does fluorine appear in RT?
A pale yellow gas (F2)
How does chlorine appear in RT?
Cl2
A green gas
How does bromine appear in RT?
An orange / brown liquid (Br2)
Vaporises easily
How does Iodine (I2) appear at RT?
A shiny grey- black crystalline solid
What are the trend of group 7 , going down the group?
7️⃣density increases
7️⃣MP/BP increase
7️⃣ reactivity decreases
What do halogens produce when reacting with metals?
Salt
Why does the reactivity decrease when going down the group?
Must gain 2 electrons
More atomic radius = weaker forces of attraction
More shielding = weaker forces of attraction
More shells , makes it harder to attract 2 electrons
Why do halogens displace other halogens?
If they are more reactive (more higher on in the group) then they kick the other out
What are some chemical and physical properties of group 0 elements
0️⃣all gasses at RT
0️⃣so un reactive (full outer shells)
0️⃣non metals
0️⃣monatomic
0️⃣low BPs
What is the trend of group 0 going down the group?
Boiling point increases (attractive forces between atoms are stronger)
Boiling point increases
What are some properties of transition metals?
Shiny when freshly cut
Good conductors of electricity
Strong
Malleable
Describe the transition metals in comparison to group 1
More dense
More stronger /harder
Higher melting points
Also less reactive
What are some chemical properties of transition metals?
💚Less reactive than group 1
💚Produce coloured ionic compounds
💚Can have multiple charges
💚Good catalyst
💚 resistant to corrosion (not so reactive)
What is the reactivity series?
Potassium
Sodium
Calcium
Magnesium
Aluminium
Zinc
Iron
Tin
Lead
What does the rate of reaction tell you?
The order of reactivity
More reactive = greater rate of hydrogen production
Do group 0 react?
NOPE
Full outer shell and so won’t easily give up or gain electrons
Which are least reactive out of group 1, group 2 and transition metals
Transition metals
How do you test for oxygen?
Place a glowing splint near the mouth of the container of gas
If oxygen is present the splint should relight
How do you test for hydrogen?
Place a lighted splint near the mouth of the container.
If hydrogen is present it should ignite with a squeaky pop
How do you test for carbon dioxide ?
Use limewater (calcium hydroxide).
If it turns cloudy when carbon dioxide is bubbled through then it is present.
White precipitate = calcium carbonate
How do you test for chlorine?
- Dampen the blue litmus paper
- Put it near, should turn red then white(bleeches )
Chlorine + water =acidic solution
What colour is lithium in the flame test?
Red
What colour is sodium in the flame test?
Yellow
What colour is potassium in the flame test?
Lilac
What colour is calcium in the flame test?
Orange-red
What colour is copper in the flame test?
Green-blue
Why do metal ions create a colour when heated?(excitation)
Energy is transferred to the electrons
They move to higher shells , and then move back down
As they do radiation is emitted in the form of visible light
How do you carry out a flame test?
- Clean Nichrome wire loop in HCL, hold it in the flame until it stops changing colour.
2.dip the loop into the test powder. - Hold it in the roaring flame and note the colour
Why is sodium hydroxide solution used in experiments?
Group 1 hydroxides are soluable in water
What colour does iron (ll) make in the sodium hydroxide tests?
Green
What colour does iron (lll) make in the sodium hydroxide tests?
Orange - brown
What colour does copper(ll) make in the sodium hydroxide tests?
Blue
What colour does calcium make in the sodium hydroxide tests?
A white precipitate that does NOT a dissolve in excess
*remains white
What colour does zinc make in the sodium hydroxide tests?
A white precipitate that DOES dissolve in excess.
Goes from white to colourless
How do you detect sulfate ions?
Add HCL
Add barium chloride
If present then should get an insoluble white precipitate (barium sulphate)
How do you detect carbonate ions?
Add a few drops of dilute hydrochloric acid
*should produce bubbles
If present there should be bubbling of carbon dioxide being released
2H+ (aq) + CO3 2-(aq) —> CO2 (g) + H2O (l)
How do you detect halide ions?
Add a few drops of nitric acids
Then add a few drops of silver nitrate solution
What colour Is the precipitate of silver chloride?
Whitw
What is the colour of silver bromide?
Cream
What is the colour of silver iodide precipitate ?
Yellow
What is the reaction for the copper hydroxide(product)?
CuSo4 (aq) + 2NaOH(aq) —> Cu(OH)2 (s) + Na2SO4 (aq)
Net ionic equation:
Cu 2+ (aq) + OH- (aq) —> cu(OH)2 (s)
What are the advantages of instrumental methods of analysis?
🟢speed
🟢accuracy : more decimal points
🟢sensitivity: a small amount can be used
How do you interpret a mass spectrometer?
The x axis (mass to charge ratio) is just the mr
1. Look at the last peak on the graph, this is the relative formula of the entire substance
What is formed when a metal and water react?
Metal + water —> metal hydroxide + hydrogen
Why might a precipitate reaction occur really fast?
The collision frequency is high
What would you observe if a Grp 1 metal is added to water?
🟣floats on surface
🟣fizzing
🟣the flame of hydrogen ignites
🟣melts as reacts
What is a metal and steam form?
🤨
Metal+ steam —> metal oxide + hydrogen
Metal + H20–> metalO + H2
Weird coz it’s water but no hydroxide
Why might some experiments be made in a fume cupboard?
The gas produced could be TOXIC
¥toxic by Britney Spears 💋
Why does the reactivity increase going down group 1 (2marks)?
🟢more shielding
🟢’outer electron’ is lost more easily
Why is nitric acid added before silver nitrate?
To make sure there are no carbonate ions present
What is a yield of a product?
The mass of the product that is made in a chemical process
What is theoretical yield?
The maximum amount of mass that is possible to be made from the given mass of reactants
How do you calculate theoretical yield?
Basically a reacting masses question:
1. From mass find mols
2. Find mols of desired thing through stoichometry
3. Convert back from mols to mass
Will be answered in grams
How do you calculate percentage Yield?
(Actual yield ➗theoretical yield)✖️100
What affects percentage yield? (!100%)
🟢transfer loss of substance
🟢reaction may not go to completion
🟢reaction may react in a different way than planned
What is atom economy?
How many atoms in the reactants form a desired product
How do you calculate atom economy?
(Sum of Mr of desired products➗sum of Mr of all products)✖️100
BALANCING NUMBERS ARE INCLUDED
What factors affect the reaction pathway?
🟡percentage yield
🟡atom economy
🟡rate of reaction
🟡usefulness of by products
🟡wether it is a reversible reaction
How do you convert between dm and cm cubed?
Cm^3: dm^3
1000:1
10cm =1dm
How do you calculate the concentration of a solution
Concentration (mol/dm^3 ) = amount in mass/mols➗volume in dm^3
How do you convert between g/dm^3 and mol/dm^3?
➗molar mass
How do you carry out a titration?
🔶biruete clamped using a glass clamp
🔶volumetric pipette to measure alkali
🔶Then put into a conical flask
🔶using a funnel put the acid in the biruette, read the bottom of the minniscous and place the set up on the floor to get at eye level
🔶take out the funnel and add indicator (phenolphthalein)in the conical flask, should be pink
🔶add the acid while swirling when it turns colourless , stop the tap. Repeat 3 times -Dripwise
🔶initial - final = titre
What is the point of a titration?
To find the concentration of the acid or alkali
How do you calculate titration questions?
1) find mols
2) do the stoichemetry
3) convert back to concentration
Mols = volume ✖️concentration
What is the rate of reaction?
How quickly products are formed/reactants used.
Amount of products are formed/reactants used.➗time taken
How do you measure the rate of reaction from a gas syringe? With different concentration
(A conical flask with a rubber bung attached to the gas syringe)
🔹measure a known volume of acid
🔹add known mass of other solute
🔹measure the volume of gas every 30s
🔹repeat with different concentrations of acid
🔹repeat using the same temperature
How do you read a volume time line graph?
At the beginning a steep gradient because more reactant particles means more successful collisions.
A flat line towards the end means that the reaction has stopped.
The gradient measures the rate of reaction
How do you calculate the mean rate of reaction (2 values)?
Do change in y ➗ change in x for
How do you calculate the instantaneous rate of reaction?
At the point draw a tanget.
Then calculate the gradient of this tangent.
How does temperature affect the rate of reaction?
🟡increases rate of reaction as particles hold move more quickly and so would collide more frequently.
🟡 these colliding particles would also have the activation energy or more
🟡therefore leading to successful collisions
Describe the disappearing cross experiment
Draw a black cross on a piece of paper and place beneath a transparent beaker. Place the reactants in the beaker and start timing , stop it when the black cross is no longer visible. Calculate the rate by doing
1➗time
How does increased concentration affect the rate of reaction?
Concentration =how much solute is dissolved in the solvent
🟣 more crowded particles
🟣 more collisions per second
🟣due to rate of collisions increasing , the rate of successful collisions increases
How does increasing pressure affect the rate of reaction?
🟣more particles per unit of volume (in the gas state the particles become more crowded )
🟣more collisions per second
🟣as rate of collisions increases the rate of successful collisions increases
HOw does the size of the reactants affect the rate of reaction.
🟣smaller the pieces, the larger the surface area
🟣more particles are exposed (more reactant particles are available for collisions)
🟣higher frequency of collisions.
🟣due to increased frequency of collisions, there is an increased frequency of successful collisions
How would you use the mass balance experiment to measure the rate of reaction?
NOT WHEN USING HYDROGEN AS TOO LIGHT
Place conical a flask with a cotton wool to avoid spitting on a mass nance and record the mass at regular intervals.
What is the effect of a catalyst on the rate of reaction?
It increases the rate of reaction without using up any of it’s own energy
How do catalysts affect the activation energy?
They provide an alternative reaction pathway , with a lower activation energy. So the particles have enough energy for their collisions to be successful.
A greater proportion of the colliding particles then have the activation energy or more.
What is dynamic equilibrium?
A reversible reaction in a closed system, when the rate of the forward reaction is equal to the rate of the reverse reaction.
The concentration of the reactants an products must be stable.
What is a reversible reaction?
A reaction where the products of the reaction can react to produce the original reactants.
What does a ‘shift in the position of equilibrium’ mean?
The side to where it shifts has a larger percentage yield (more is made).
Eg: a shift to the left makes more reactants
A shift to the right makes more products
How does pressure change the position of Equilibrium?
Increasing the pressure will cause a shift to the side with less GAS mols. Because a higher pressure means less area.
How does temperature shift the position the equilibrium ?
Then through Le chatilers principal, the system will try to counteract this change as it wants to go back to before.
If there is an increase in temperature.
The system will want to get rid of this extra heat and so will perform an endothermic reaction, as it absorbs heat from the surroundings.
How does concentration shift the position of equilibrium?
Then through Le chatilers principal, the system will try to counteract this change as it wants to go back to
If the concentration of a substance has been increased then the position of equilibrium will be moved to the opposite side away from it.
What effect do catalyst have on the position of equilibrium ?
They don’t have any effect. They only increase the rate and make it a more efficient process
Why might a manufacturer compromise on temperature?
Cannot make to low because of activation energy and rate of reaction.
Cannot make too high because it’s expensive
Why might a manufacturer compromise on pressure ?
High pressure requires tough reaction vessels which can be quiet expensive
Low pressure is cheaper to generate
What are concordat titres?
Titres that are within 0.1of each other
When do gases occupy the same volume?
When they are all at room temperature and pressure
How do you handle gas calculations?
Volume = 24 (concentration) ✖️mols
Why do to measure the bottom of a minniscous ?
To avoid a parallax error
Why are indicators such as phenolphthalein used?
There is a sudden colour change as opposed to a gradual change
Why should industrial process have the highest atom economy possible?
To the reduce the production of unwanted products.
To make the process more sustainable
What does it mean for the particles to have successful collisions?
The particles have the activation energy
What is the cotton wool used for in the mass scale rate of reaction experiment?
The cotton wool prevents spitting. BUT allows the gases to escape from the flask , no worry
How could titrations be improved
🔵swirling flask, ensures mixing
🔵use a white tile underneath to see end point clearly
🔵 add drop-wise, to see colour change in one drop