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    Can anyone solve this please?
    Thnx
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    Hello everyone!Could anyone please explain me why the answer is B ?- A sample of swimming pool water contains 0.482 ppm of chlorine. This is equal to a percentage of:A. 0.000482B. 0.0000482C. 0.00000482D. 0.000000482
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    (Original post by waleedlat)
    0.482------->10^6
    ?------------>100
    oh I see haha.. thanks!
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    (Original post by imnoteinstein)
    https://110d0b1a7b584219c71ba4cfe896...0Chemistry.pdf
    Q9, answers A but why is the temp change the same? if e=mct then shouldnt the heat evolved be more bc the "mass" (volume) has increased?
    I think its because the ratio of HCl and NaOH hasn't changed, whether it is 10cm3 or 50cm3, the ratio of their masses is still 1:1 so the heat evolved would be the same.
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    (Original post by waleedlat)
    Can anyone solve this please?
    Thnx
    The question is asking for the possible combinations of the isotopes to form a O2+ ion. These are the possible combinations and the m/e:

    O16 - O16 = 32
    O16 - O17 =33
    O16 - O18 = 34
    O17 - O16 = 33
    O17 - O17 = 34
    O17 - O18 = 35
    O18 - O16 = 34
    O18 - O17 = 35
    O18 - O18 = 36

    But the combinations producing the same m/e are counted as one. Hence there are 5 peaks with different m/e peaks. B is the answer.
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    (Original post by waleedlat)
    Can anyone solve this please?
    Thnx
    the anwer is 6
    O16- O16
    O17-O17
    O18-O18
    O16-O18
    O17-O16
    O18-O17
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    (Original post by Sandy_Vega30)
    The question is asking for the possible combinations of the isotopes to form a O2+ ion. These are the possible combinations and the m/e:

    O16 - O16 = 32
    O16 - O17 =33
    O16 - O18 = 34
    O17 - O16 = 33
    O17 - O17 = 34
    O17 - O18 = 35
    O18 - O16 = 34
    O18 - O17 = 35
    O18 - O18 = 36

    But the combinations producing the same m/e are counted as one. Hence there are 5 peaks with different m/e peaks. B is the answer.
    tour anwer is wrong it is 6 not 5 check my answer and you will figure out ur mistake
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    (Original post by Sandy_Vega30)
    The question is asking for the possible combinations of the isotopes to form a O2+ ion. These are the possible combinations and the m/e:

    O16 - O16 = 32
    O16 - O17 =33
    O16 - O18 = 34
    O17 - O16 = 33
    O17 - O17 = 34
    O17 - O18 = 35
    O18 - O16 = 34
    O18 - O17 = 35
    O18 - O18 = 36

    But the combinations producing the same m/e are counted as one. Hence there are 5 peaks with different m/e peaks. B is the answer.
    Thank you
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    i have another question please help
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    (Original post by katenell)
    the anwer is 6
    O16- O16
    O17-O17
    O18-O18
    O16-O18
    O17-O16
    O18-O17
    answer is b not c
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    (Original post by katenell)
    tour anwer is wrong it is 6 not 5 check my answer and you will figure out ur mistake
    This is the 2nd Question of the Jan 2016 paper. The answer is B.
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    (Original post by waleedlat)
    i have another question please help
    Alkene + H2 ----> Alkane

    Moles of H2 : 19.2/24 = 0.8

    Mole ratio of Alkene: H2 is 0.2: 0.8 which is 1:4.
    So for this alkene, 4H2 molecules are added. That makes 8 hydrogen atoms. To break 1 double bond, 2 hydrogen atoms are need. Therefore, find how many double bonds are broken with 8 hydrogen atoms. The answer is 4 double bonds (A).
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    ok so im not very clear with using E=mct so Id appreciate if someone confirmed/corrected this:
    so when we burn something (like propane etc), we use the 'mass' of thw WATER bec it is the water thats being heated?

    and in a neutralisation reaction, the mass is sum of the volumes of acid and alkali. And if we need to find the MOLAR enthalpy, we divide by the moles of WATER formed?
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    https://110d0b1a7b584219c71ba4cfe896...0Chemistry.pdf

    question 3, why cant it be C? the empirical and molecular formula could be the same
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    (Original post by imnoteinstein)
    https://110d0b1a7b584219c71ba4cfe896...0Chemistry.pdf

    question 3, why cant it be C? the empirical and molecular formula could be the same
    Molecular formulas tell you how many atoms of each element are in a compound, and empirical formulas tell you the simplest or most reduced ratio of elements in a compound. If a compound's molecular formula cannot be reduced any more, then the empirical formula is the same as the molecular formula.
    But in this case, there is an option of C4H10 whose n is 4. This clearly makes C2H5 the empirical formula and C4H10 the molecular formula.
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    Could anyone please help me with this:
    So I have a typical scientific casio calculator, but it always gives me answers in the standard form, for example 3 x 10^-3 . How do I change it to 0.003 ?
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    (Original post by imnoteinstein)
    ok so im not very clear with using E=mct so Id appreciate if someone confirmed/corrected this:
    so when we burn something (like propane etc), we use the 'mass' of thw WATER bec it is the water thats being heated?

    and in a neutralisation reaction, the mass is sum of the volumes of acid and alkali. And if we need to find the MOLAR enthalpy, we divide by the moles of WATER formed?
    Yes, we use the mass of the water being heated because the energy from burning propane is being transferred to a Known Mass of Water, hence we are finding the energy transferred to a specific mass of WATER.

    Yes, in a neutralisation reaction, the mass is the sum of volumes of the acid and alkali.

    To find Molar enthalpy, you do not divide by the no. of moles of water formed, you divide by the moles of acid or alkali ( Usually, they use the same concentration and volume of the acid and alkali so they have the same moles).
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    (Original post by Sandy_Vega30)
    Molecular formulas tell you how many atoms of each element are in a compound, and empirical formulas tell you the simplest or most reduced ratio of elements in a compound. If a compound's molecular formula cannot be reduced any more, then the empirical formula is the same as the molecular formula.
    But in this case, there is an option of C4H10 whose n is 4. This clearly makes C2H5 the empirical formula and C4H10 the molecular formula.
    thanks but i think the reason is that c2h5 doesnt exist haha! nothing suggests which ones molecular but the fact that c2h5 isnt a thing :')
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    (Original post by Sandy_Vega30)
    Yes, we use the mass of the water being heated because the energy from burning propane is being transferred to a Known Mass of Water, hence we are finding the energy transferred to a specific mass of WATER.

    Yes, in a neutralisation reaction, the mass is the sum of volumes of the acid and alkali.

    To find Molar enthalpy, you do not divide by the no. of moles of water formed, you divide by the moles of acid or alkali ( Usually, they use the same concentration and volume of the acid and alkali so they have the same moles).
    wb when they're different? :O
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    (Original post by baebae)
    Could anyone please help me with this:
    So I have a typical scientific casio calculator, but it always gives me answers in the standard form, for example 3 x 10^-3 . How do I change it to 0.003 ?
    Press shift and the key that says "ENG" until you reach the required value.
 
 
 
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