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[Alx2]

Q: A 5g tablet contains sodium carbonate. The tablet was crushed then reacted with 20mL, 0.1M HCl. The excess acid was titrated against 0.1M NaOH needing 5mL. Calculate % of sodium carbonate in the tablet



thanks in advance

 

[deswa1]

Q: A 5g tablet contains sodium carbonate. The tablet was crushed then reacted with 20mL, 0.1M HCl. The excess acid was titrated against 0.1M NaOH needing 5mL. Calculate % of sodium carbonate in the tablet



thanks in advance

For these questions, work backwards. First find out the volume of excess HCl you have using the titration information. Then you know how must acid was left to react with the sodium carbonate and then you solve.

 

[someth1ng]

If the HCl and NaOH was 0.1M and it needed 5mL to complete the titration then Na2CO3 effectively neutralised 15mL of the 0.1M HCl.

Note: if the concentration of NaOH was different to the concentration of HCl, you must compare the number of moles of NaOH against the number of HCl.

1. Calculate the number of moles of HCl using n=c/V where V=0.015mL and c=0.1
2. Write a balanced equation
Na2CO3+2HCl-->2NaCl+H2O+CO2 (add the states)
3. Calculate the number of moles of Na2CO3 --> you need half the moles of Na2CO2 as there are moles of HCl.
4. Convert moles of Na2CO3 into grams using n=W/MW

 

[bleakarcher]

If the HCl and NaOH was 0.1M and it needed 5mL to complete the titration then Na2CO3 effectively neutralised 15mL of the 0.1M HCl.

Note: if the concentration of NaOH was different to the concentration of HCl, you must compare the number of moles of NaOH against the number of HCl.

1. Calculate the number of moles of HCl using n=c/V where V=0.015mL and c=0.1
2. Write a balanced equation
Na2CO3+2HCl-->2NaCl+H2O+CO2 (add the states)
3. Calculate the number of moles of Na2CO3 --> you need half the moles of Na2CO2 as there are moles of HCl.
4. Convert moles of Na2CO3 into grams using n=W/MW

n=cV

 

[someth1ng]

n=cV

Yeah, that's what I meant - my bad. Just muddled up my train of thought (I blame using an iPod ).

 

[bleakarcher]

Yeah, that's what I meant - my bad. Just muddled up my train of thought (I blame using an iPod ).

lol just wanted to point it out so the OP doesn't get confused

 

[Alx2]

oooo got it now lol thanks :]

btw just wondering is there a specific rule for naming cfc;s /halons that stuff?

my teacher sed something about alphabtical order but u put the most electrongative first ? o.o

like fluorine b4 cl even though cl is more alphabet

 

[deswa1]

oooo got it now lol thanks :]

btw just wondering is there a specific rule for naming cfc;s /halons that stuff?

my teacher sed something about alphabtical order but u put the most electrongative first ? o.o

like fluorine b4 cl even though cl is more alphabet

Is this naming isomers? You look at the electronegativity in order to determine which carbon is numbered 1 (assuming that counting from both ends gives the same number when you add up the 'other stuff's position). You always write in alphabetical order

 

[DrWho94]

Heyy just curious where you got the 0.015 L shouldn't it be 0.02 L?

 

[someth1ng]

Depends on which naming system you are talking about.

For: CCl2F2
Sytematic Name: Dichlorodifluoromethane
CFC Name: Freon-12

For: C2H2Br2F2
The systematic name depends on the structure of the molecule.
Systematic Name: 1,2-dibromo-2,2-difluoroethane (example only)
Halon Name: Halon-2202

For CFCs (carbon, hydrogen, fluoine and chlorine), the naming scheme is:

Prefix is Freon-
To get the number that follows "Freon-" (suffix), you do this:
1. Find the number of carbons atoms (first number)
2. Find the number of hydrogen atoms
3. Find the number of fluorine atoms (the rest are chlorine atoms)
This makes a 3 digit number, you'll most likely be asking why my freon number is only 2 digits. What you do now is subtract 90
4. Add the number behind "Freon-"

For Halons (carbon, hydrogen, fluorine, chlorine and bromine) the naming scheme is:

Prefix is Halon-
To get the number that follows "Halon-", you do this:
1. Find the number of carbons atoms (first number)
2. Find the number of fluorine atoms
3. Find the number of chlorine atoms
4. Find the number of bromine atoms (the rest are hydrogen)
That makes a 4 digit number when in order you get something like Halon-2022

Note: the 5th number is actually iodine but you probably don't need to know that

 

[someth1ng]

hey why is it 0.015 L ?
shudnt be 0.020L ?

5mL of NaOH was needed to complete the titration so effectively, 15mL of the acid was neutralised the Na2CO3.