Chemistry C2 Probemas

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How do electrons form compounds?
React together by gaining or losing electrons.
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What group do elements in group 1 react with?
Group 7
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What happens when elements in group 1 react with group 7 and what does this form?
They lose one electron to gain a stable electronic structure of a noble gas.
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What are ionic compounds held together by and what is this claled?
Strong forces and this is call ionic bonding.
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What do the charges on an ionic compound always do?
Cancel each other out so there's no outstanding charges (such as + or -)
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What do group 1 metals and group 2 metals form?
1+ ions and 2+ ions
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What do group 1 NON-metals and group 2 NON-metals form?
-1 and -2 ions.
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How are Covalent bonds formed?
When atoms share pairs of electrons.
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What is a common attribute of substances containing covalent bonds?
Simple molescules but mostly have giant covalent structures.
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Name 2 examples of giant covalent structures.
Graphite, Diamond (#kieronb), Sillica
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What are the properties of giant covalent structures?
Very high melting points and Variable conductivity
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What can we think of metallic bonding as?
Postively charged metal ions held together by electrons in the outermost shell.
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What is required to break strong ionic bonds?
Large amounts of energy
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What do ionic compounds have and why?
High melting points as a lot of energy is required to break the,.
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Why do ionic compounds conduct electricity when dissolved?
Ions can move freely in a liquid.
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What are the properties of substances made up of simple molecules?
Low melting and boiling points.
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Why are substances made up of simple molecules not conduct electricity?
They cannot carry any electrical charge as they have no overall charge.
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Why is graphite slippery (in terms of a covalent structure)?
No covalent bonds between layers thus can slide over each other.
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Why can graphite conduct electricity?
The delocalised electrons along it's layers.
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What happens if a shape memory alloy is deformed then heated?
Turns back to it's original shape.
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What is nanoscience?
Study of small particles between 1 and 100 nano-metres in size.
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What some uses of nanoscience?
Used in sun creams and deodrants as they go deep into the skin.
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What is the relative mass of proton and neutrons?
1
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What is the atomic number of a substance?
Number of protons (equals number of electrons)
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What is the mass number of a atom?
Total of protons and neutrons in nucleus.
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What are isotopes?
Atoms with the same element with different number of NEUTRONS.
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What is the mole of a substance?
It's Rel Form Mass, in Grams.
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What can the R.A.M of the elenet in a compound and formula be used to work out?
It's percentage composition of each element/substance in the compound. (such as 40% magnesium, 60% uranium)
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What is empirical forumula?
a formula giving the proportions of the elements present in a compound but not the actual numbers or arrangement of atoms.
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What do balanced symbol equations tell us?
Number of moles involved in a chemical reaction.
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What does the yield of a chemical reaction mean?
How much of the product is made.
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Formula for percentage yield =
( amount produced / max amount possible ) x 100%
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Why do very few chemical reactions have 100% yield?
Reactants may give unexpected products; reactants may not be entirely pure, or reaction may be reversible.
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Why is it important to maximise yield and minimise energy wasted?
Conserve the earths limited resources.
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What is a reversible reaction?
A reversible reaction is a reaction where the reactants form products, which react together to give the reactants back.
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Why are additives added to food?
Improve it's appearance, taste, and how long it'll keep (shelf life).
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What are advantages and disadvantages of using modern instruments to analyse product/food?
A: Quick, small samples only needed, very accurate D: Expensive, requires special training.
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How can compounds in a mixture be seperated?
Using gas chromatography.
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What is gas chromatography?
Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition.
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Once a compound is separated by gas chromatography, how compounds be identifies?
Mass spectrometer.
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What's the process for gas chromatography?
Mixture vaporised > Gas moved through coiled column > Analysed by mass spectrometer
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How can we find the rate of chemical reaction?
Amount of reactants used up over time.
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What must particles do before they can react?
Collide with a certain amount of energy.
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What is activation energy?
The minimum amount of energy which the reactants must possess in order to undergo a reaction.
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How can you increase the rate of chemical reactions in a solid and why?
Increase surface area as this increases frequency and quantity of particle collisions.
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How can you make reactions happen more quickly?
Increase the tempature.
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Why does increasing the temperature of a reaction speed it up?
Particles become more 'energetic' so collide more.
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What's another way that you can increase the rate of reaction?
Increase the concentration of reactants or increasing pressure of reacting gasses.
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What does a catalyst do?
Speed up rate of chemical reaction.
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Is the catalyst used up in a chemical reaction?
No.
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What is a perk of a catalyst?
Lowers costs and speeds up reaction
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What types of things as traditional catalysts?
Transitional metals or compounds.
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Disadvantages to traditional catalysts?
Produce waste, can be toxic and damage enviroment if they escape.
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What is a exothermic reaction?
An exothermic reaction is a chemical reaction that releases energy by light or heat. It is the opposite of an endothermic reaction.
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Express a exothermic in a chemical equation.
Expressed in a chemical equation: reactants → products + energy.
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What is a endothermic reaction?
Endothermic reactions take in energy from the surroundings.
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Name a industrial use of an exothermic reaction:
Hand warmers of self-heating cans.
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Name a industrial use of an endothermic reaction:
Instant cold packs
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What do acids produce when added to water?
H+ ions.
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What are bases?
Substances which neutralise acids.
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What is a alkali?
Soluble hydroxide.
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What do alkalis produce when we add them to water?
OH- ions
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Is pure water, neutral, alkali, or acid?
Neutral.
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What is the reaction called when we react a acid with a base?
A neutralisation reaction.
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How can salts be made?
Reacting a suitable metal with a acid.
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What's the word equation for making a salt?
acid + base ---------> a salt + water
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How can an insoluble salt be made?
Reacting two solutions to produce a precipitate.
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Why is precipitation important industrially?
Way of removing metal ions from wastewater.
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What is electrolysis?
The breaking down of a substance using electricity.
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When can ionic compounds be electrolysed and why?
When their molten or in a solution because therr ions are free to move to the electrodes.
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What happens in regards to the electrodes during electrolysis?
Ions moved towards the oppositely charged electrodes.
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What happens at the electrodes?
Negatives ions are oxidised while positive ions are produced.
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What happens if electrolysis occurs during water?
The less reactive element between hydrogen (water) and the metal is produced at the negative electrode. At the positive electrode we get O2 gas.
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During the manufacture of aluminium, what metal is electrolysed?
Aluminium oxide.
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During the manufacture of aluminium, what is the Aluminium oxide mixed with to lower it's melting point?
Molten cryolite.
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What are some uses of aluminium?
Pans, power cables, aeroplanes, drank cans, bombs.
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What 3 products do we get when we electrolyse brine?
Chlorine gas; hydrogen and sodium hydroxide solution.
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What CAN WE USE THE 3 products we get when we electrolyse brine for?
Chlorine to make bleach, hydrogen to make margarine, and Sodium Hydroxide to make bleach, and paper.
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Why would we electroplate a object?
Improve appearance, and to protect their surface.
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What is electroplating? (made by DG)
To coat a metal object by electrolytic deposition with chromium, silver, or another metal.
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Other cards in this set

Card 2

Front

What group do elements in group 1 react with?

Back

Group 7

Card 3

Front

What happens when elements in group 1 react with group 7 and what does this form?

Back

Preview of the front of card 3

Card 4

Front

What are ionic compounds held together by and what is this claled?

Back

Preview of the front of card 4

Card 5

Front

What do the charges on an ionic compound always do?

Back

Preview of the front of card 5
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