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Description
Flashcards by vittoria howard, updated more than 1 year ago
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Created by vittoria howard
almost 10 years ago
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| Question | Answer |
| C3 | C3 |
| what is an exothermic reaction? | one which gives out energy |
| what is an endothermic reaction? | one which takes in energy |
| what is an example of an exothermic reaction? | burning fuels |
| what is an example of an endothermic reaction? | thermal decomposition |
| how can you measure the amount of energy released in a chemical reaction? | measure the temperature of each of the reactants then mix them in a polystyrene cup and measure the temperature of the solution. |
| is adding an acid to an alkali endo or exothermic? | exothermic |
| is dissolving ammonium nitrate in water an endo or exothermic reaction? | endothermic |
| what must be supplied to break bonds? | energy |
| what is released when bonds are broken? | energy |
| is breaking bonds endo or exothermic? | energy is supplied so it is endothermic |
| is forming bonds endo or exothermic? | energy is released so it is exothermic |
| what is the SHC of water? | 4.2 j/g/C |
| what is the equation for energy transferred? | energy transferred (j)= mass of water(g) x SHC of water(4.2j/h/C) x temperature change (C) |
| what is the equation for energy given out per gram of fuel? | energy released (j) / mass of fuel burned (g) |
| what is an example of a slow reaction? | rusting of iron or chemical weathering (acid rain) |
| what is an example of a moderately paced reaction? | a metal (eg magnesium) reacting with a dilute acid to perform a gentle stream of bubbles |
| what is an example of a fast reaction? | burning |
| what is an example of a really fast reaction? | an explosion |
| what are the two ways to measure how fast a gas is produced in a reaction? | measure the change in mass by performing the experiment on scales and recording the drop in gas at regular intervals. You can also use a gas syringe to measure at regular intervals. With both methods you need to plot your results on a graph. |
| what does the rate of a collision depend on? | collision frequency and energy transferred in a collision |
| what does the amount of product you get from a reaction depend on? | how much product you start with |
| more reactant means more what? | particles- these go on to have more reactions so create more products. |
| what is the amount of product you get directly proportional to? | the amount of limiting reactant (the reactant that is completely used up) |
| what does it mean when we say a reactant is in excess? | there is still some left after the limiting reactant has stopped the reaction |
| what increases the amointt of collisions in a reaction? | increasing the temperature- the particles are faster with more energy increasing the concentration/ pressure- the particles are more crowded smaller solid particles/ bigger surface area-other particles can get to it more easily |
| what increases the number of successful collisions? | a catalyst- it gives the reacting particles a a surface to stick o where they can bump in to each other, and reduces the amount of energy needed by the particles before they react. The overall number of collisions isn't increased but the number of successful ones is. |
| what is relative atomic mass? (Big A, Little r) | bigger of the two numbers for an element on the periodic table |
| what is relative formula mass? (Big M, Little r) | all the relative atomic masses of a compound added together eg- MgCl2= Mg+(2 x Cl) =24+(2 x 35.5) = 95 |
| compounds with brackets in... | Example: find the relative formula mass for calcium hydroxide, Ca(OH)2 Method: the small number after the bracket means you multiply everything in the bracket by 2 |
| what always happens to the mass in a chemical reaction? | it is conserved |
| what does conserved mean? | no atoms are destroyed and no atoms are created |
| what is the result of this? | equal numbers and types of atoms on each side of a reaction equation. Because of this, no mass is lost or gained |
| what are the steps to calculate masses in a reaction? | 1) write out the balanced equation 2) work out Mr- for the two but you want 3 )apply the rule: divide to get one, then multiply to get all (you need to apply the rule to the substance they give you first, then the other one) |
| what is atom economy? | the percentage of reactants turned into useful products |
| what is the equation for atom economy? | total Mr of desired products/ x 100 total Mr of all products |
| What does a 100% atom economy mean? | all the atoms in the reactants have been turned into useful/ desired products |
| what does a higher atom economy show? | a greener process |
| what is high atom economy better for? | profits and the environment |
| what are the problems with low atom economy? | use up reactions very quickly and create waste, aren't profitable as raw materials are expensive, and waste can be expensive to remove. |
| what is the best solution for this problem? | find a use for the waste products rather than throwing them away. There's often more than one way to make the reactant you want so choose a reaction with useful 'by-products' rather than useless ones |
| which reactions have the highest atom economy? | ones with only one product- they have an atom economy of 100% |
| what does percentage yield compare? | actual and predicted yield |
| what is the equation for percentage yield? | actual yield (g) / x100 predicted yield (g) |
| what does a 100% yield mean? | you got all the product you expected to get |
| what does a 0% yield mean? | no products were made |
| why do you never get a 100% yield in real life? | some product or reactant is always lost along the way, no matter how big the scale of production. |
| what four things could be a reason for not having 100% yield? | Evaporation- liquids may evaporate when heated Not all reactants react to make product-in reversible reactions, the product can turn back into reactants Filtration- you always loose a bit of liquid or solid when separating them Transferring liquids |
| when does batch production operate? | only at certain times |
| when does continuous production operate? | all the time |
| why is batch production often the most cost-effective way to produce small quantities of different drugs to order? | its flexible so several different products can be made with the same equipment and start up costs are fairly low as the equipment can be bought off the shelf. |
| what are the disadvantages of batch production? | its labour-intensive as the equipment needs to be set up and manually controlled for each batch and then cleaned out at the end and it can be tricky to keep the same quality from batch to batch |
| what are the advantages of continuous process? | production never stops so you don't waste time emptying the reactor and setting it up again, it runs automatically so you only need to interfere if something goes wrong and the quality of the product is very consistent |
| what is the disadvantage of continuous process? | the start up costs are huge and it isn't cost effective to run at less than full capacity |
| why do pharmaceutical drugs often cost a lot? | research and development- it takes about £900 million to develop a new drug trialing- animal and human trials manufacture- batch process is labour intensive and there are other costs such as energy and raw materials. Many products need to be extracted from plants which is very expensive |
| how do you extract a substance from a plant? | crush it, boil it, dissolve it in a suitable solvent then separate it by chromotography and extract the chemical you want |
| how do you test for purity using chromotography? | pure substances won't be separated by chromotography, it will all move as one blob and have a specific melting and boiling point. eg. pure ice melts at 0 degrees C and pure water boils at 100 degrees C. If the substance is impure it will have a higher/ lower point.. eg ice that melts at -2 may have salt in it |
| what are 2 allotropes of carbon? | diamond and graphite |
| what is diamond used in? | jewellery and cutting tools |
| what properties make diamonds good for jewellery? | they are lustrous (sparkly) and colourless |
| what properties makes diamond good for cutting tools? | it is hard and has a high melting point |
| what makes diamond hard? | each carbon atom has 4 covalent bonds in a very rigid giant covalent structure. |
| why does diamond have a high melting point? | all the strong covalent bonds require a lot of energy to be broken |
| why doesnt diamond conduct electricity? | it has no free electrons |
| why is the structure of graphite unique? | each carbon atom only creates 3 covalent bonds, creating sheets of carbon atoms which are free to slide over each other. |
| what makes graphite ideal for use in a pencil? | the layers are held together weakly so they are slippery and can be rubbed off on to paper to leave a black mark |
| why does graphite have a high melting point? | the covalent bonds need a lot of energy to break them |
| why does carbon conduct electricity? | because only 3 out of its 4 outer electrons are used in bonds, there are lots of delocalised (spare) electrons that can move |
| why can you get giant molecular structures of diamond and graphite? | carbon can form lots of covalent bonds with itself |
| what do the many covalent bonds mean for the gian molecule structure? | it is strong, has a high melting point and can't dissolve in water. |
| why don't giant molecular structures of carbon usually conduct electricity? | they don't have any free electrons- graphite is the exception |
| what is a fullerene? | molecules of carbon shaped like a hollow ball or closed tube |
| what is buckminsterfullerene? | the smallest fullerene- it has 60 atoms of carbon joined in a ball. |
| what can fullerenes do to other molecules? | cage them- the fullerene structure forms around another atom or molecule, which is then trapped inside. |
| what do you get when you join fullerenes? | nanotubes |
| what are nanotubes? | tiny hollow carbon tubes |
| what can nanotubes be used for? | they have a huge surface area so they could help make great industrial catalysts- individual catalyst molecules could be attached to the nanotubes |
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