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Author Topic: CHEM AND BIO HELP AND TIPS HERE  (Read 366565 times)

Offline jellybeans

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1365 on: May 21, 2010, 05:34:33 pm »
heyyyy;
does anybody know if white 'precipitation' is acceptable for the zinc cation test??? like .. is 'precipitation' acceptable instead of 'precipitate' :S :S :S
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Offline Ivo

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1366 on: May 21, 2010, 05:45:50 pm »
Quote from: jellybeans on May 21, 2010, 05:34:33 pm
heyyyy;
does anybody know if white 'precipitation' is acceptable for the zinc cation test??? like .. is 'precipitation' acceptable instead of 'precipitate' :S :S :S

Say "white precipitate".  Precipitation is a process in forming a precipitate.  Like adding silver nitrate (soluble) to sodium chloride (soluble) gives silver chloride (insoluble - precipitate) and sodium nitrate (soluble).  Therefore, this reaction is a precipitation reaction but one of the products formed is a precipitate.  Get it?
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Offline nerdvictim

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1367 on: May 21, 2010, 06:22:45 pm »
i have a question  ???

can someone please tell me the uses, and dangers of over use of fertilzers pleasee :D:D thank youuu

oh oh anndd the importance of magnesium and nitrates in the soil and what will happen to the plant if the soil lack them.  ???  ??? :)
thanx in advance 
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Offline Ivo

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1368 on: May 21, 2010, 06:38:33 pm »
Quote from: nerdvictim on May 21, 2010, 06:22:45 pm
i have a question  ???

can someone please tell me the uses, and dangers of over use of fertilzers pleasee :D:D thank youuu

oh oh anndd the importance of magnesium and nitrates in the soil and what will happen to the plant if the soil lack them.  ???  ??? :)
thanx in advance  

Dangers of overuse:  Eutrophication

Importance of magnesium: production of chlorophyll - for photosynthesis.  Deficiency symptoms: yellow leaves.

Importance of nitrates: makes amino acids, therefore proteins for growth and tissue repair.  Deficiency symptoms: short and thin stems, roots etc.

Has this helped?
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Offline nerdvictim

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1369 on: May 21, 2010, 07:05:36 pm »
Quote from: Ivo on May 21, 2010, 06:38:33 pm
Dangers of overuse:  Eutrophication

Importance of magnesium: production of chlorophyll - for photosynthesis.  Deficiency symptoms: yellow leaves.

Importance of nitrates: makes amino acids, therefore proteins for growth and tissue repair.  Deficiency symptoms: short and thin stems, roots etc.

Has this helped?

yes!! thank you so much :D:D
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Offline $H00t!N& $t@r

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1370 on: May 21, 2010, 07:49:42 pm »
i need help with chemistry paper 1 M/J 2008  q15 and 19. i know the answer ofc cz i have the ms but i dont understand it so can you explain
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1371 on: May 21, 2010, 07:59:41 pm »
Quote from: Shooting Star on May 21, 2010, 07:49:42 pm
i need help with chemistry paper 1 M/J 2008  q15 and 19. i know the answer ofc cz i have the ms but i dont understand it so can you explain

Q 15 C

not endothermic because rise in temp by 2 *C
neutralisation because acid + base gives salt and water
ZnO + HCl ==> ZnCl2 + H2O

Q 19 D

The process occurring involves the equilibrium between chromate(VI), dichromate(VI) and hydrogen ions


The addition of hydroxide ions causes the concentration of hydrogen ions to decrease, and this brings the equilibrium back to the left-hand side, regenerating yellow chromate(VI) ions. Under alkaline conditions and the orange dichromate(VI) ions predominate in acidic solutions.

Examination of oxidation numbers will show that chromium remains in the +6 oxidation state throughout.

SOURCE : http://www.practicalchemistry.org/experiments/an-equilibrium-involving-chromatevi-and-dichromatevi-ions,284,EX.html
« Last Edit: May 21, 2010, 08:08:35 pm by ~VIN1094~ »
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Offline $H00t!N& $t@r

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1372 on: May 21, 2010, 08:36:37 pm »
ok... i want to get one thing clear.. lets say i add some copper sulphate solution in a beaker then i add zinc powder to it. this reaction would be exothermic right? so does it mean that the beaker would be cold when touched?? or would it be hot???  exo-thermic...heat is given out shouldnt the beaker be cold???

and for en-dothermic..  shouldnt the beaker be hot when touched cz heat is taken in
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nid404

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1373 on: May 21, 2010, 08:40:11 pm »
naah naah...

Ohk...ill clear this.

When it's exo...it gives out heat to the surrounding, which includes the beaker it is in....so it's warmer
When it's endo....it takes in heat from the surrounding, which includes heat from the beaker, this lowers the beaker temp, making it cooler
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1374 on: May 21, 2010, 08:50:44 pm »
yup nid's right .. got it??

adding zinc to copper sulfate is totally different .. its displacement reaction .. its SALT + METAL ---> METAL + SALT

CuSO4(aq) + Zn(s) ---> ZnSO4 + Cu(s)

This reaction is exothermic but ur question tht u;ve asked is different!! (ques 15)

its ACID + BASE ----> SALT + WATER

which is neutralisation and exothermic .. don't wanna confuse u jus keep in mind  ACID + BASE ----> SALT + WATER is neutralisation and SALT + METAL ---> METAL + SALT is displacement .. careful not all neutralisation  are exothermic .. they usually state the temperature difference in the ques
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Offline $H00t!N& $t@r

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1375 on: May 21, 2010, 08:51:32 pm »
ohhh i seee  so the beaker is included and heat is taken in or given out to the surroundings. i get itt. thnxx  ;)
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"If A equals success, then the formula is:
A=X+Y+Z, X is work. Y is play. Z is keep your mouth shut"- Albert Einstein

Offline $H00t!N& $t@r

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1376 on: May 21, 2010, 08:55:41 pm »
Quote from: ~VIN1094~ on May 21, 2010, 08:50:44 pm
yup nid's right .. got it??

adding zinc to copper sulfate is totally different .. its displacement reaction .. its SALT + METAL ---> METAL + SALT

CuSO4(aq) + Zn(s) ---> ZnSO4 + Cu(s)

This reaction is exothermic but ur question tht u;ve asked is different!! (ques 15)

its ACID + BASE ----> SALT + WATER

which is neutralisation and exothermic .. don't wanna confuse u jus keep in mind  ACID + BASE ----> SALT + WATER is neutralisation and SALT + METAL ---> METAL + SALT is displacement .. careful not all neutralisation  are exothermic .. they usually state the temperature difference in the ques

i know that vin but i just wanted to clear a doubt i had. By the way Thanks for the answer but i get 80% of it. i dint get the part about the chromate thing
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"If A equals success, then the formula is:
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Offline 2010

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1377 on: May 22, 2010, 01:30:20 am »
Quote from: Shooting Star on May 21, 2010, 08:55:41 pm
i know that vin but i just wanted to clear a doubt i had. By the way Thanks for the answer but i get 80% of it. i dint get the part about the chromate thing
please someone help with biology artificial and natural selection
it would be really great if someone could prepare some sort of general answer which i could write for selection questions of natural selection and evolution
please also some sort of answer on artificial selection
i have read the book 2 times but just dont seem to get his topic
so please help me and do it as soon as possible only 1 day to go
thankssssss
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Offline guMnam

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1378 on: May 22, 2010, 05:37:34 am »
Quote from: ~VIN1094~ on May 21, 2010, 08:50:44 pm
yup nid's right .. got it??

adding zinc to copper sulfate is totally different .. its displacement reaction .. its SALT + METAL ---> METAL + SALT

CuSO4(aq) + Zn(s) ---> ZnSO4 + Cu(s)

This reaction is exothermic but ur question tht u;ve asked is different!! (ques 15)

its ACID + BASE ----> SALT + WATER

which is neutralisation and exothermic .. don't wanna confuse u jus keep in mind  ACID + BASE ----> SALT + WATER is neutralisation and SALT + METAL ---> METAL + SALT is displacement .. careful not all neutralisation  are exothermic .. they usually state the temperature difference in the ques
hey my teacher said tht all neutralisation reactions are exothermic ?????
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nid404

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1379 on: May 22, 2010, 05:45:47 am »
Yes all neutralization reactions are exothermic. Heat of neutralization is -57kJ/mol
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