C2 Flash Cards

Pregunta	Respuesta
Who First Suggested that Electrons orbit the Nucleus?	Rutherford
Image: rutherford (image/png)	This shows the Rutherford Experiment. The research team fired alpha particles at gold foil, Whilst most travelled straight through (showing that the atom is mostly empty space), some were deflected and came off at an angle and a few even came out backwards. This made Rutherford realise that atoms must have a solid core, he called this the 'Nucleus'.
Name one difference and one similarity between an atom and an isotope.	Isotopes have a slightly diiferent number of neutrons in their nucleus. For example there is Potassium-39 and Potassium-40. However, as they have the same number of electrons they each react in the same way.
How can isotopes be used to calculate the age of something?	Some elements have radioactive isotopes which decay over time. By knowing how quickly an isotope decays (or it's half-life), scientists can calculate the age of an object by checking the amount of radioactive, non-decayed atom is left. For example Carbon-14 is used for objects suspected of being up to 60,000 years old.
Work out the relative formula mass of water (H2O).	(2x1) + 16 = 18
How do chemists make it easier for them to count the relative formula mass of an atom or molecule?	They say that the atomic or formula mass is measured in grams a mole.
Why are noble gases unreactive?	Because they have a full outer shell of electrons.
How does an atom become an ion?	The atom must ionically bond with another atom (metal and non-metal). This means that it either loses or gains one or more electron(s) to give itself a + or - charge.
Why can ionic compounds conduct electricity when dissolved in water or molten, but not when solid?	This is because when solid the ions cannot move around and carry the electric current. However when they are melted they are free to do so.
The first Group 1 elements were discovered in 1800. However they were not separated from their compunds until 1875. Why is this?	Because electrolysis wasn't invented till 1875.
What is the charge of a HALOGEN?	-1
Chlorine is a highly toxic gas which is used to kill bacteria in the water we drink. Why does the chlorine in the water not kill us as well?	Because not enough is used to harm humans.
Why are the melting and boiling points of an ion very high?	This is because the bonds of an ion are very strong so it takes a lot of energy to break them.
What is the difference between a single and a double bond?	Single bonds only share one electron each (two in total). Double bonds share two (four in total).
What is the charge of both atoms in a covalent bond?	Positive
Do Covalent bonds have high or low melting and boiling points and why?	They are low because there are only very weak intermolecular forces between the atoms.
If a compound is easy-to-melt and a poor conductor of electricity, what type of bonding does it have?	Covalent
Give 3 examples of a covalent lattice and their use.	Diamond: Drill bits Graphite: Pencil led Silicon Dioxide: Sandpaper
What is the difference in the structures of a thermosoftening and a thermosetting polymer?	Thermosoftening: A tangle of smooth chains that can easily slide past each other. Thermosetting: Each chain has side chains and connections to other chains, making it difficult for them to slide past each other.
Why does metallic bonding allow the compound to conduct electrons?	This is because it contains lots of delocalised electrons to carry the current.
What is an alloy?	A mixture of two or more metal elements.
What do these 'smart' materials do? Photochromic Thermochromic Shape memory	Photochromic: changes colour according to intensity of light. Thermochromic: change colour according to temperature. Shape Memory: when warmed, will return to it's original shape.
How could buckminsterfullerene (C60), be used in the future to treat cancer infections?	Molecules of highly toxic drugs could be trapped inside the sphere and carried to the infected site to kill cancer cells.
How can chromatography be used to check what food colourings have been used in a sample?	This can be done by separating the food additives on some chromatography paper and doing the same with some other food colourings. Then you would check if any of the colourings matched up with the spots separated from the food.
Name each of these chemical reactions: 1. Gaining Oxygen 2. Losing Oxygen 3. Reacting an acid with an alkali or base. 4. Reacting two soluble compounds to form an insoluble product. 5. Using electricity to split a liquid or a solution.	1. Oxidation 2. Reduction 3. Neutralisation 4. Precipitation 5. Electrolysis
Name the 5 factors that affect a rate of reaction.	Temperature, Pressure, Concentration, Surface area and Catalysts.
If you were told that 1.27g of copper was used to maken 1.59g of copper oxide, how would you work out the formula for copper oxide?	1. Calculate the mass of oxygen used (1.59-1.27 = 0.32g) 2. Divide the mass of copper and the mass of oxygen by their respective relative atomic mass (1.27/63.5 = 0.02) and (0.32/16 = 0.02). 3. Divide each result by the smallest, i.e. 0.02. This gives the ratio of atoms in the formula (0.02/0.02 = 1 copper and 0.02/0.02 = 1 oxygen) CuO.
What is the equation for calculating the Percentage Yield?	Actual Yield / Theoretical Yield x 100
What is the advantage of using an ore that is 75% pure over an ore that is 25% pure?	This is because the purer ore gives a higher percentage yield. This makes economic sense as less raw materials are needed and less is wasted creating unwanted product.
What does a double-headed arrow for a reaction mean?	This means that it is reversible.
Name one equation to determine the rate of reaction.	Rate of reaction = amount of product formed / time taken
How do you calculate the rate of reaction for a graph at a given point?	Calculate the graph's gradient at that point.
True or False? In a reaction, every time two particles collide they react.	False. The particles must collide with enough energy for reaction to take place. The minimum energy for this to happen is called the activation energy.
True or False? The higher the concentration of a solution, the faster the particles will react.	True. As there are more reactants in the same volume, the chances of the particles colliding with sufficient activation energy is higher.
In what reaction is iron used as a catalyst?	The Haber Process
How does a catalyst help speed up the rate of reaction?	It manages to enable particles to react with a lower activation energy.
Name two factors that chemists need to take into account when planning an industrial process (reaction).	Temperature, Pressure or the required catalyst.
Do exothermic reactions emit heat into it's surroundings or absorb heat from around it?	It emits heat. This results in the products having a lower level of chemical energy than the reactants.
What is produced when a base reacts with an acid?	A salt and water.
Are neutralisation reactions exothermic or endothermic?	Exothermic.
If Ammonia solution is dissolved in water, what is produced?	Ammonium hydroxide solution.
If sulphuric acid was used in a reaction to create a salt, what would the end of the salt's name be?	Sulphate (e.g. Copper Sulphate)
A salt is what type of compound?	Ionic. It has positive ions for two metals and negative ions of two non-metals.
How would you identify if a halogen compound is present?	Add silver nitrate.
Why can electrolysis not be done with mains electricity?	This is because mains electricity is an alternating current. Electrolysis requires a direct current.
What is produced with the electrolysis of sodium chloride solution.	Hydrogen, Sodium Hydroxide and Chlorine.
During electrolysis, what happens to the positively charged ions?	They move towards the negatively charged electrode (or cathode) and are reduced.

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