Warning: Illegal string offset 'html' in /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php on line 909

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 114

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 127

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 136

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 137

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 141
2004 - Written Paper - Q8 - HSN forum

Jump to content


2004 - Written Paper - Q8


2 replies to this topic

#1 sarmad

    Good Effort

  • Members
  • PipPipPip
  • 76 posts
  • Gender:Male

Posted 25 May 2006 - 03:07 PM

Hi,
could someone please explain to me how to get the answer to Q8, the enthalpy of neutralisation question, i got the answer to come out as 65 which is wrong !

#2 Michael

    Site Swot

  • Members
  • PipPipPipPip
  • 237 posts
  • Location:Glasgow
  • Gender:Male

Posted 25 May 2006 - 03:37 PM

The Enthalpy of neutralisation is the energy required to produce one mole of water.

NaOH + HCl ---> NaCl + H2O
1mole NaOH ----> 1mole H2O

E=cmΔT
=4.18x0.04x6.5 temp change = 25.5 - average of the other solns=6.5
=1.0868

n=cv
n=1x0.02
n=0.02 moles

0.02moles ------->1.0868
1 mole -----------> -54.34 kjmol-1

#3 Nathan

    Fully Fledged Genius

  • Members
  • PipPipPipPipPipPipPip
  • 1,736 posts
  • Location:Aberdeen, Scotland
  • Gender:Male

Posted 25 May 2006 - 03:42 PM

NaOH + HCl ---> NaCl + H2O

*remember that enthalpy of neutralisation is the energy required to produce 1 mole of water*

moles of NaOH = 0.020 x 1 = 0.02 moles
moles of HCl = 0.020 x 1 = 0.02 moles

avg start temp = (18+20)/2 = 19
delta.gif H = 25.5-19 = 6.5

delta.gif H = cm delta.gif T
= -4.18 x 0.04 x 6.5
= -1.0868 for 0.02 moles water

1/0.02 = 50 implies.gif multiply delta.gif H by 50

delta.gif H = -1.0868 x 50
= -54.34 kj mol-1

(rounded to -54 in answer scheme)





1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users