Chemistry Paper 1

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What is meant by an endothermic reaction, give an example?
It takes in energy from the surroundings, more energy goes in than comes out Example: Thermal decomposition
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What is meant by an exothermic reaction, give an example?
It gives out energy to the surroundings, more energy is released than put in Example: Combustion
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Explain what happens in a chemical cell
The electrons flow from the more reactive metal to the less reactive metal. The more reactive metal acts as the negative terminal providing electrons to the external circuit. The bigger the difference in reactivity, the bigger the voltage of the cell
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What happens in the first stage of a hydrogen fuel cell and what is the equation?
1. Hydrogen enters at the cathode and reacts to form a hydrogen ion and electron, forming an electric current.
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What happens in the second stage of a hydrogen fuel cell and what is the equation?
2. Oxygen enters at the anode and reacts with the electrolyte and electrons to form hydroxide ions which is attracted to the hydrogen ions to form water
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What are 2 advantages and 2 disadvantages of hydrogen fuel cells?
Advantages: -doesn't need to be electrically recharged, no pollutants produced, can be made in a variety of sizes Disadvantages: Hydrogen is highly flammable, Hydrogen is difficult to store, Hydrogen is sometimes produced non-renewably
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Does breaking bonds release or absorb energy, and vice-versa?
Breaking absorbs, Forming releases
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Explain the difference between strong and weak acids
-Strong acids completely ionise in water -Therefore there is a higher concentration of H+ ions in the solution -Gives it a low pH of about 1 -Weak acids partially ionise so lower concentration of H+ ions in solution
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How does the concentration of H+ ions affect the pH?
-As the concentration of H+ ions decrease by a factor of 10, the pH value increases by 1. A solution of pH 4 is 1000 times weaker than a solution of pH 1
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What are the characteristics of bases?
-Neutralise acids -Generally insoluble -Metal oxides and carbonates -All alkalis are bases but are soluble and form hydroxide ions
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What does OIL RIG stand for?
Oxidation is Loss (of electrons) Reduction is Gain(of electrons)
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What charge do the anode and cathode have and which ions are attracted to them?
Anode is the positive electrode so will attract negative ions. Cathode is the negative electrode so will attract positive ions
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What is the order in which negative ions are attracted to the anode?
1. Halide ions (halogen) 2. Hydroxide ion (forms oxygen) 3. Other negative ions
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What is the order of reactivity?
Please Send Charlie's Monkeys And (Carbon) Zebras In Lead (Hydrogen) Cages Securely Guarded
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What type of compounds can be electrolysed and why?
Molten or aqueous ionic compounds as their ions are free to move and carry a charge
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What products are formed when an acid and a base or alkali react?
A salt and water
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What products are formed when an acid and a carbonate react?
A salt, carbon dioxide and water
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How do you know the charge on a transition metal?
It is always positive and the size of the charge is given by the roman numeral i.e Copper (II) ion has a charge of Cu2+
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Which titration is Methyl Orange used for and what colours does it turn
Strong acid + Weak alkali (or strong and strong) -Red in acid -Yellow in alkali
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Which titration is Phenolphthalein used for and what colours does it turn
Weak acid + Strong alkali (or strong and strong) -Colourless in acid -Pink in alkali
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What is Avogadro's constant and what is it used for?
6.02 x 10^23, it is used to work out the number of atoms, molecules or ions in a mole of any substance
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Why are alloys harder than pure metals?
Because in an alloy the regular layers of a pure material are distorted by atoms of different sizes therefore the layers cannot easily slide over each over or bend
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What are the properties of diamond and silicon dioxide?
-Giant covalent structures -High melting and boiling points -Insoluble in water -Doesn't conduct electricity as there are no delocalised electrons -Hard, tetrahedral structure
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What are the properties of graphite?
-Giant covalent structure -High melting and boiling point -Insoluble in water -Conducts electricity and thermal energy as there are delocalised electrons which are free to carry a charge -No covalent bonds between layers so they can slide over
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What are the limitations of the particle models of solids, liquids and gases?
-Assumes particles are made of solid spheres with no forces operating between them -The particles are often different sizes and not spherical -Atoms are mostly empty space so are not solid as the spheres indicate
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What does a chromatography experiment tell you about a substance?
It's solubility in that solvent. The further up the paper it travels, the more soluble it is in that solvent.
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What are the properties of the alkali metals?
-Reactivity increases going down the group -Low density, first 3 float on water -Soft -Shiny, silvery when first cut but quickly tarnish -Fairly low m.p and b.p, decrease going down the group -React with water to create hydrogen and metal hydroxide
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What are the properties of the halogens?
-Reactivity decreases down the group -Low m.p + b.p which increase going down the group -Poor conductors of heat & electricity -Diatomic molecules -Form single negative ions with metals -Form covalent compounds by sharing electrons with non-metals
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What are the three things that control electrostatic attraction?
-The distance between the outmost electrons and nucleus -The number of occupied inner shells, which provide a shielding effect -The size of the positive charge on the nucleus(nuclear charge) -Further down the group it is easier to lose electrons and
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What are the properties of the transition metals?
-Much higher melting points and densities compared to alkali metals -Strong and hard -Not very reactive, don't react vigorously with oxygen or water -Form ions with different charges and often form coloured compounds -Important industrial catalysts
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What colours are the compounds: 1. Copper(II) sulfate 2 Nickel(II) Carbonate 3. Chromium(III) oxide 4. Manganese (II) chloride
1. Blue 2. Pale green 3. Dark green 4. Pale pink
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What colour is the final solution of the reaction, Cl2 (aq) + 2KI(aq) -> I2(aq) + 2KCl(aq), explain?
Brown as Iodine is now an atom and therefore keeps its characteristics however the chlorine is part of a compound so doesn't display its pure atomic properties
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In an aqueous solution will the more or less reactive ions be attracted to the cathode?
Less reactive, generally hydrogen but not always
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Where is the proton number on a element and what does it show?
It is the smaller number. Sometimes called the atomic number. It shows how many protons and therefore how many electrons are in an element
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What is Ohm's law and which components follow it?
-The current through a resistor at constant temperature is directly proportional to the P.D across the resistor -Resistor follows it -Bulb and lamp do not follow Ohm's law
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What happens to the resistance in series and parallel circuits?
V=IR, Parallel- V is the same and I is shared(lower) so R is higher. Series-V is shared(lower) and I is the same so R is lower, Resistance is added together
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What happens to the current and P.D in a parallel circuit?
-The current in a parallel circuit is shared between the components in each branch, the overall current is the sum of the current across each component -The P.D is equal across all branches in the parallel circuit
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What happens to the current, P.D in a series circuit?
-The current is the same all the way around the circuit -The potential difference is shared between components, the total p.d in the circuit is the sum of the P.D of each cell
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What will happen when a polythene and perspex rod are rubbed with a dry cloth?
Polythene becomes negatively charged as it gains electrons from the cloth. Perspex will become positively charged as it transfers electrons from the rod to the cloth. Their charges are equal and opposite
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What is CCS?
Carbon capture and storage, it is technology that could be used to stop CO2 emissions into the atmosphere. The carbon dioxide is captured and pumped through pipes below the earth into holes such as where oil, gas or coal has been mined from
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Card 2

Front

What is meant by an exothermic reaction, give an example?

Back

It gives out energy to the surroundings, more energy is released than put in Example: Combustion

Card 3

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Explain what happens in a chemical cell

Back

Preview of the front of card 3

Card 4

Front

What happens in the first stage of a hydrogen fuel cell and what is the equation?

Back

Preview of the front of card 4

Card 5

Front

What happens in the second stage of a hydrogen fuel cell and what is the equation?

Back

Preview of the front of card 5
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