Turn on thread page Beta

Chemistry Help watch

Announcements
    • Thread Starter
    Offline

    0
    ReputationRep:
    Hey I was just wondering If anyone can help with these 2 questions

    1)Why is carbon-12 the only atom with a relative atomic mass which is an exact whole number?

    2) Calculate the mass of 1 mol of H+ ions ( but then in the question it states the weight of one electron - which i dont understand as i thought a H+ ion had no electrons, just a single proton? so why state the mass of an electron?)

    Cheers.
    Offline

    7
    ReputationRep:
    (Original post by Rob92)
    Hey I was just wondering If anyone can help with these 2 questions

    1)Why is carbon-12 the only atom with a relative atomic mass which is an exact whole number?

    2) Calculate the mass of 1 mol of H+ ions ( but then in the question it states the weight of one electron - which i dont understand as i thought a H+ ion had no electroncs, just a single proton? so why state the mass of an electron?)

    Cheers.
    I'm not 100% on question one, so I better hadn't corrupt your mind with false info.

    But question (2) is quite simple. They've given you the weight of an electron, because to deduce the weight of a proton, you'll need to subtract this value from the weight of a normal Hydrogen atom (these are composed of one electron and one proton). This will give you the weight of a proton. Then, multiply this vale with Avagadro's number (6.02 X 10^23), which'll give you the weight of one mole of H+.
    Offline

    15
    ReputationRep:
    The answer to question 1 lies in the definiton of relative atomic mass:

    The mass of 1 mole of an element on a scale where the mass of 1 mole of Carbon atoms is 12 units.

    Therefore, the scale is standardised by Carbon, which has a given value of 12, everything else will be slightly, if not, significantly off a whole number.
    Offline

    14
    ReputationRep:
    (Original post by Rob92)
    1)Why is carbon-12 the only atom with a relative atomic mass which is an exact whole number?.
    One carbon-12 atom is an exact whole number by international agreement because one atom of the carbon-12 isotope has been assigned a mass of 12 atomic mass units.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: October 20, 2008

University open days

  • University of Warwick
    Undergraduate Open Days Undergraduate
    Sat, 20 Oct '18
  • University of Sheffield
    Undergraduate Open Days Undergraduate
    Sat, 20 Oct '18
  • Edge Hill University
    Faculty of Health and Social Care Undergraduate
    Sat, 20 Oct '18
Poll
Who is most responsible for your success at university

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.