Hey there! Sign in to join this conversationNew here? Join for free

chemistry help please Watch

Announcements
    Offline

    3
    ReputationRep:
    (Original post by J_riley18)
    Okay is 74.093 right?
    74 is precise enough.

    Now work out the relative formula mass of calcium phosphate. Post your answer.
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by TeachChemistry)
    74 is precise enough.

    Now work out the relative formula mass of calcium phosphate. Post your answer.
    Is 182.234 right for calcium phosphate
    Offline

    3
    ReputationRep:
    (Original post by J_riley18)
    Is 182.234 right for calcium phosphate
    No. Look at the formula. There are 3 calcium, 2 phosphorus and 8 oxygen. Make sure you can see how this is the case and give a revised answer.
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by TeachChemistry)
    No. Look at the formula. There are 3 calcium, 2 phosphorus and 8 oxygen. Make sure you can see how this is the case and give a revised answer.
    Is 310 right?
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by TeachChemistry)
    No. Look at the formula. There are 3 calcium, 2 phosphorus and 8 oxygen. Make sure you can see how this is the case and give a revised answer.
    Is 310 right?
    Offline

    3
    ReputationRep:
    (Original post by J_riley18)
    Is 310 right?
    Yes.

    Now use the equation below to work out the moles of calcium hydroxide you have in 5 g

    Moles X relative formula mass = mass
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by TeachChemistry)
    Yes.

    Now use the equation below to work out the moles of calcium hydroxide you have in 5 g
    Moles X relative formula mass = mass
    Is 370 g/mol correct
    Offline

    3
    ReputationRep:
    (Original post by J_riley18)
    Is 370 g/mol correct
    You need to work out the moles. You have the mass and you have the relative formula mass from a few posts back. You need to rearrange the equation I have (hopefully) reminded you of.

    Try again.
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by TeachChemistry)
    You need to work out the moles. You have the mass and you have the relative formula mass from a few posts back. You need to rearrange the equation I have (hopefully) reminded you of.

    Try again.
    Is 1.34 mols correct
    Offline

    3
    ReputationRep:
    (Original post by J_riley18)
    Is 1.34 mols correct
    I cannot see where this number comes from.

    You have 5 g and correctly said that the relative formula mass was 74.

    Think again.
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by TeachChemistry)
    I cannot see where this number comes from.

    You have 5 g and correctly said that the relative formula mass was 74.

    Think again.
    I did 5g/mol × 74 = 370 is that right?
    Offline

    3
    ReputationRep:
    (Original post by J_riley18)
    I did 5g/mol × 74 = 370 is that right?
    No. Here's a worked answer because it is bedtime for me now. Make sure you follow it through. Ask tomorrow if unsure.
    Attached Images
     
    Offline

    17
    ReputationRep:
    >mfw undergraduate chemistry

    This would have been a standard question when I was 14/15 years old
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Should Spain allow Catalonia to declare independence?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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

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