GCSE Level Chemistry Student Answers
i need to know the answer to this!
1. Write the symbol equation for photosynthesis and respiration. Also write which is endothermic and exothermic.
6H2O + 6CO2 ----------> C6H12O6+ 6O2 photosynthesis
C6H12O6 + 6O2 = 6CO2 + 6H2O + Energy Respiration
Photosynthesis is an example of an endothermic chemical reaction.
In this process, plants use the energy from the sun to convert carbon dioxide and water into glucose and oxygen. This reaction requires 15MJ of energy (sunlight) for every kilogram of glucose that is produced.
Exothermic reactions are reactions that give out heat energy.
Respiration is an exothermic reaction. Aerobic respiration is the breakdown of food, using oxygen, to release energy.
Hope this helps.
For my GCSE chemistry coursework I have to investigate the effects temperature has on rate of reaction. We have to warm sodium thiosulphate up in a test tube at different temeperatures and then measure the temperature when it is mixed with hychloric acid. Could you please help me with the method and could you also explain the Arrhenius Equation and the 10oc rule. Thanks.
Oh heres another one and it seems in much much more detail. hope it helps again love Z
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i would appreciate any help
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Fe3+ will be more stable because, Fe has an electronic subshell structure of 3D6 and 4S2. When it loses two electrons to form 2+ the electrons are first lost from the 4S subshell. When it loses 3 electrons the electronic configuration becomes 3D5 4S0. All you need to know is that a complete or half filled D subshell gives stability. Since 3+ form of Iron will give that stability Fe3+ is more stable.
Just as side knowledge D subshells can take 10 electrons. A half or completely filled D subshell gives stability
" such as the erroneous belief that water conducts electricity, which it doesn't. It's the impurities in the water that conduct electricity. Since Distilled Water is Pure Sterile Water with nothing else present, it does not conduct electricity. "
" Yes, and this is correllated to the ability of hard water to conduct electricity. Distilled Water will not conduct electricity(even when 2 parts per million inorganic minerals or less are present). Water with 5 parts inorganic content per million parts water(or more) will conduct electricity, completing a simple circuit and lighting a tester bulb. The higher the inorganic content is in a per million count, the less effectively water transmits organic minerals to tissue sites. Bottled water, tapwater, reverse-osmosis filtered water, and carbon-block filtered water(when tested) will conduct electricity, substantiating that these are not the best carriers for mineral-transport and mineral-absorption(Muehling 1994). Tapwater in the USA has been shown to contain 19 "inorganic metals of concern"(1994 Safe Water Drinking Act), for which maximum contaminant levels have been set.(Tone 1994) Most American tapwater tested falls between the ranges of 350 parts per million to over 1000 parts per million total contaminants.(Colgan 1993) "
Hi, I know this is a bit of a problem considering I take my chemistry mock next week but what is an ion? and an iomer? and also how do I work out moles?
An ion is a species with a charge, either do to the gain or loss of electrons. Examples include Na+ (loss of an electron) Cl- (gain of an electron) and Mg 2+ (loss of two electrons)
You probably mistaked ''iomer'' for an ''isomer'' . An isomer is a molecule with a same molecular formula but different structural formula. For example alkenes: but-1 ene and but-2-ene both have the molecular formula of C4H8 (4 carbons and 8 hydrogens). However, when it comes to writing their structural formula, but-1-ene is written as CH3CH2CH=CH2, and but-2-ene as CH3CH=CHCH3. Notice the number (i.e. but-1-ene) just shows the position of the double bond in alkenes.
In order to work out the number of moles - you need to know 3 equations:
1) Number of moles = Mass/Molar mass
2) Number of moles = Concentration x volume.
3) (gaseous moles) = Volume of gas (in dm3)/ 24
Note: Equation 3 only applies to a gas!
An example of each:
Using equation 1:
How many moles are there in 0.8g of copper ii oxide?
Ans: Work out the molar mass of copper ii oxide using a periodic table. Cu = 64, O = 16
So molar mass = 80.
Now just plug numbers in the equation:
Number of moles = Mass/Molar mass = 0.8/80 = 0.01moles
Using equation 2:
How many moles of sodium chloride are there in 200cm3 of 2 M solution:
Ans: The equation we are using is Number of moles = Concentration x volume. But first, we need to convert the volume from cm3 into dm3. Do this by dividing it by 1000. So 200cm3 in dm3 = 200/1000 = 0.2 dm3
Now just plug the numbers into the equation:
Number of moles = Concentration x volume = 2 x 0.2 = 0.4 moles
Note that the concentration is expressed in 'M' or 'mol dm-3'. Both mean the same thing.
Using equation 3:
How many moles of hydrogen molecules are there in 48cm3 of the gas.
Ans: The equation we use is: number of moles = Volume of gas (in dm3)/ 24
We have the volume of gas, which is 48cm3. This needs to be converted into dm3. Just as above, 48cm3 into dm3 = 48/1000 = 0.048 dm3.
Now just plug the numbers into the equation:
number of moles = Volume of gas (in dm3)/ 24 = 0.048/24 = 0.002 moles.
Notice we can use all three equations to work out the number of moles of one substance, when we have the concentration of another.
Hope this helps. Best regards.