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Few Easy AS Chem Questions ...
1) Describe the pattern of electrical conductivity
Searched many textbooks and found nothing.
2) The mass of the isotope 79Br is 1.31 x 10^-22 g. The molar mass of 79Br is 79.0gmol^-1.
Use this indormation to calculate a value for the Avogadro constant. Give your answer to 3 sig figs.
3) A small piece of freshly cut sodium was added to propan-2-ol give 2 observations which wld be made?
i gave one as Effervesence, could i say to the other that the solution goes warm or something?
4) Suggest one reason wht its difficult to measure enthalpy change of reaction directly by experiment?
Thats all, thank you for those who help
+rep
Searched many textbooks and found nothing.
2) The mass of the isotope 79Br is 1.31 x 10^-22 g. The molar mass of 79Br is 79.0gmol^-1.
Use this indormation to calculate a value for the Avogadro constant. Give your answer to 3 sig figs.
3) A small piece of freshly cut sodium was added to propan-2-ol give 2 observations which wld be made?
i gave one as Effervesence, could i say to the other that the solution goes warm or something?
4) Suggest one reason wht its difficult to measure enthalpy change of reaction directly by experiment?
Thats all, thank you for those who help
+rep
The-Godfather
1) Describe the pattern of electrical conductivity
Searched many textbooks and found nothing.
2) The mass of the isotope 79Br is 1.31 x 10^-22 g. The molar mass of 79Br is 79.0gmol^-1.
Use this indormation to calculate a value for the Avogadro constant. Give your answer to 3 sig figs.
3) A small piece of freshly cut sodium was added to propan-2-ol give 2 observations which wld be made?
i gave one as Effervesence, could i say to the other that the solution goes warm or something?
4) Suggest one reason wht its difficult to measure enthalpy change of reaction directly by experiment?
Thats all, thank you for those who help +rep
Searched many textbooks and found nothing.
2) The mass of the isotope 79Br is 1.31 x 10^-22 g. The molar mass of 79Br is 79.0gmol^-1.
Use this indormation to calculate a value for the Avogadro constant. Give your answer to 3 sig figs.
3) A small piece of freshly cut sodium was added to propan-2-ol give 2 observations which wld be made?
i gave one as Effervesence, could i say to the other that the solution goes warm or something?
4) Suggest one reason wht its difficult to measure enthalpy change of reaction directly by experiment?
Thats all, thank you for those who help
+rep1) - pattern with reference to what? I would guess that elements with more electrons will be more conductive as of more charge carriers - this will only work for metals i think as for metals the electrons are free to move ( metallic structure)
2) - 1 mole of any substacne always contains 6.02 x 10 ^23 atoms. The mass of 1 mole of the Br isotope is 79 g and the mass of Br isotope atom is 1.31 x 10^-22 g.
79 / 1.31 x 10^-22 g = 6.03 x 10^23 atoms
3) Not sure. To know if it was heated up you would need to know the enthalpy change for the reaction
4) - entahlpy change is for gaseous products and the reactants you use may not be in gaseous state and you can talk about heat loss if you were using the heating water experiment when using alcohol as a fuel.
1) http://en.wikipedia.org/wiki/Electrical_conduction and
http://en.wikipedia.org/wiki/Current_%28electricity%29
also have a look in some Physics textbook
2) all you need is to divide the mole mass of Br atoms by the mass of one atom.
79g / 1,31 *10^-22g = 6,023 * 10^23
3) sodium reacts with propanol:
2C3H7OH+ 2Na -----> H2 + 2C3H7ONa
so one observation can be that the solution gets warm and the second one that a gas is produced
4) I guess it's because enthalpy in constant pressure is the amount of heat used or produced in the reaction. Some energy is always lost to the environment, because you can't completely isolate the reaction. So if you measure enthalpy it's never 100% accurate
http://en.wikipedia.org/wiki/Current_%28electricity%29
also have a look in some Physics textbook
2) all you need is to divide the mole mass of Br atoms by the mass of one atom.
79g / 1,31 *10^-22g = 6,023 * 10^23
3) sodium reacts with propanol:
2C3H7OH+ 2Na -----> H2 + 2C3H7ONa
so one observation can be that the solution gets warm and the second one that a gas is produced
4) I guess it's because enthalpy in constant pressure is the amount of heat used or produced in the reaction. Some energy is always lost to the environment, because you can't completely isolate the reaction. So if you measure enthalpy it's never 100% accurate
pure_joy
1) http://en.wikipedia.org/wiki/Electrical_conduction and
http://en.wikipedia.org/wiki/Current_%28electricity%29
also have a look in some Physics textbook
2) all you need is to divide the mole mass of Br atoms by the mass of one atom.
79g / 1,31 *10^-22g = 6,023 * 10^23
3) sodium reacts with propanol:
2C3H7OH+ 2Na -----> H2 + 2C3H7Na
so one observation can be that the solution gets warm and the second one that a gas is produced
4) I guess it's because enthalpy in constant pressure is the amount of heat used or produced in the reaction. Some energy is always lost to the environment, because you can't completely isolate the reaction. So if you measure enthalpy it's never 100% accurate
http://en.wikipedia.org/wiki/Current_%28electricity%29
also have a look in some Physics textbook
2) all you need is to divide the mole mass of Br atoms by the mass of one atom.
79g / 1,31 *10^-22g = 6,023 * 10^23
3) sodium reacts with propanol:
2C3H7OH+ 2Na -----> H2 + 2C3H7Na
so one observation can be that the solution gets warm and the second one that a gas is produced
4) I guess it's because enthalpy in constant pressure is the amount of heat used or produced in the reaction. Some energy is always lost to the environment, because you can't completely isolate the reaction. So if you measure enthalpy it's never 100% accurate
3) - are you sure 3 is right because it's not balanced --> there aren't any oxygens on the product side.
thanks. I haven't noticed it,of course there should be an oxygen- sodium binds with propanol instead of hydrogen
btw.
he needs to find the number of atoms in one mole- that is what the Avodagro constant is
btw.
2) - 1 mole of any substacne always contains 6.02 x 10 ^23 atoms. The mass of 1 mole of the Br isotope is 79 g and the mass of Br isotope atom is 1.31 x 10^-22 g
he needs to find the number of atoms in one mole- that is what the Avodagro constant is
Einsteinium
1) - pattern with reference to what? I would guess that elements with more electrons will be more conductive as of more charge carriers - this will only work for metals i think as for metals the electrons are free to move ( metallic structure)
it just says,
The electrical conductivites of the elements in the periodic table show periodicity.
Then says define periodicity which i can do, then asks
Describe the pattern of electrical conductivity.
So according to wat you said, whichever element that has the most electrons must have the highest conductivity, so the trend must be from left to right and top to bottom the elements have greater electrical conductivity?
Please correct me if thats wrong, thanks.
http://en.wikipedia.org/wiki/Electrical_conduction#Solids_.28including_insulating_solids.29
edit: on a second thought this link may not be very relevant...
edit: on a second thought this link may not be very relevant...
The-Godfather
it just says,
The electrical conductivites of the elements in the periodic table show periodicity.
Then says define periodicity which i can do, then asks
Describe the pattern of electrical conductivity.
So according to wat you said, whichever element that has the most electrons must have the highest conductivity, so the trend must be from left to right and top to bottom the elements have greater electrical conductivity?
Please correct me if thats wrong, thanks.
The electrical conductivites of the elements in the periodic table show periodicity.
Then says define periodicity which i can do, then asks
Describe the pattern of electrical conductivity.
So according to wat you said, whichever element that has the most electrons must have the highest conductivity, so the trend must be from left to right and top to bottom the elements have greater electrical conductivity?
Please correct me if thats wrong, thanks.
I remember now. Across a period it increases and then decreases and according to my revision guide it says this too, I think it might decrease when the period goes into the P block.
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