Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    9
    ReputationRep:
    Attachment 695062Is the answer to b 7.87 gdm-3
    Offline

    14
    ReputationRep:
    (Original post by HN786)
    Attachment 695062Is the answer to b 7.87 gdm-3
    I'm sorry, I couldnt find the attachment...
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by Iluv2edgedsword)
    I'm sorry, I couldnt find the attachment...
    This work?Name:  IMG_2544.jpg
Views: 14
Size:  495.8 KB
    Offline

    18
    ReputationRep:
    (Original post by HN786)
    This work?
    I got 3.94 gdm^-3 (half of what you got):

    0.0528 moldm^-3 * 0.025 dm^3 = 0.001321 mol of sodium carbonate
    Each mole of sodium carbonate requires 2 moles of hydrochloric acid, so 0.001321*2 = 0.2642 moles of hydrocholoric acid were used.
    0.2642 mol / 0.0245 dm^3 = 0.1078 moldm^-3 hydrochloric acid
    RFM of hydrochloric acid is 1 + 35.5 = 36.5 (your periodic table may have slightly different values - use those).
    0.1078 moldm^-3 * 36.5 gmol^-1 = 3.94 gdm^-3.
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by TheMindGarage)
    I got 3.94 gdm^-3 (half of what you got):

    0.0528 moldm^-3 * 0.025 dm^3 = 0.001321 mol of sodium carbonate
    Each mole of sodium carbonate requires 2 moles of hydrochloric acid, so 0.001321*2 = 0.2642 moles of hydrocholoric acid were used.
    0.2642 mol / 0.0245 dm^3 = 0.1078 moldm^-3 hydrochloric acid
    RFM of hydrochloric acid is 1 + 35.5 = 36.5 (your periodic table may have slightly different values - use those).
    0.1078 moldm^-3 * 36.5 gmol^-1 = 3.94 gdm^-3.
    Why would you multiply the moles of sodium carbonate by 0.025
    Offline

    2
    ReputationRep:
    Hi, just to jump in. They multiplied the concentration (0.0528M) by the volume (0.025dm3 or 25cm3) in order to get the moles, as moles = conc * vol
    Offline

    20
    ReputationRep:
    1.4g = 1.4/106 = 0.013 moles

    0.013 moles in 250ml

    therefore there is 4x0.013 moles of of sodium carbonate in 1dm^3 = 0.052 mol/dm^3

    25ml of 0.052 molar solution of sodium carbonate reacts with 24.5 ml HCl.

    The molarity of the acid is 25x2x0.052/24.5 = 0.106mol/dm^3

    There is 0.106x36.5g = 3.87g/dm^3

    My answer has fewer rounding errors.
    Offline

    18
    ReputationRep:
    (Original post by TheMindGarage)
    I got 3.94 gdm^-3 (half of what you got):

    0.0528 moldm^-3 * 0.025 dm^3 = 0.001321 mol of sodium carbonate
    Each mole of sodium carbonate requires 2 moles of hydrochloric acid, so 0.001321*2 = 0.2642 moles of hydrocholoric acid were used.
    0.2642 mol / 0.0245 dm^3 = 0.1078 moldm^-3 hydrochloric acid
    RFM of hydrochloric acid is 1 + 35.5 = 36.5 (your periodic table may have slightly different values - use those).
    0.1078 moldm^-3 * 36.5 gmol^-1 = 3.94 gdm^-3.
    Because you used 25cm^3 of it. 25cm^3 = 0.025dm^3.
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by TheMindGarage)
    Because you used 25cm^3 of it. 25cm^3 = 0.025dm^3.
    Just wanted to check if i got these questions right, my answer for a was 0.0432moldm3
    My answer to b was 9.72gm3
    Name:  IMG_2549.jpg
Views: 10
Size:  285.2 KB
 
 
 
  • 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
    Did TEF Bronze Award affect your UCAS choices?
  • 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.