What mass of sodium carbonate would be required to prepare 250 ml of 0.1 M sodium car Watch

wag12k12dunkno
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What mass of sodium carbonate would be required to prepare 250 ml of 0.1 M sodium carbonate?

please help and explain it to me, i really dont understand
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Munrot07
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you have a volume and a concentration so work out the moles n = (C x V)/1000

Then work out the mass m = n x Mr (you know that sodium carbonate is Na2CO3 so use the periodic table to work out the Mr)
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4evershinee
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(Original post by wag12k12dunkno)
What mass of sodium carbonate would be required to prepare 250 ml of 0.1 M sodium carbonate?

please help and explain it to me, i really dont understand
Okay, so here is how you do it
First, you find the moles of sodium carbonate in the given solution.
moles=concentraton x volume (n=cv)
=0.1mol/dm3 x (250/1000)dm3
(0.1M = 0.1mol/dm3 and converting 250ml into dm3 by dividing by 1000)
=0.025mol

Next, you find out the molecular mass of Na2CO3=
( 23 x 2) + 12 + (16 x 3)
= 46 + 12 + 48
=106 (g/mol)

Then, you find out the mass of Na2CO3 needed to give .025 mol (the amount of moles in the solution)
moles= mass / molar mass
Therefore, mass = moles X molar mass
=0.025 x 106
2.65g

Hope this helps
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wag12k12dunkno
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(Original post by Munrot07)
you have a volume and a concentration so work out the moles n = (C x V)/1000

Then work out the mass m = n x Mr (you know that sodium carbonate is NaCO3 so use the periodic table to work out the Mr)
thanks but isnt sodium carbonate na2co3 and so will it be 0.025*106=2.56g! and also can you explain how it all works
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wag12k12dunkno
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(Original post by 4evershinee)
Okay, so here is how you do it
First, you find the moles of sodium carbonate in the given solution.
moles=concentraton x volume (n=cv)
=0.1mol/dm3 x (250/1000)dm3
(0.1M = 0.1mol/dm3 and converting 250ml into dm3 by dividing by 1000)
=0.025mol

Next, you find out the molecular mass of Na2CO3=
( 23 x 2) + 12 + (16 x 3)
= 46 + 12 + 48
=106 (g/mol)

Then, you find out the mass of Na2CO3 needed to give .025 mol (the amount of moles in the solution)
moles= mass / molar mass
Therefore, mass = moles X molar mass
=0.025 x 106
2.65g

Hope this helps
thanks so much! i just did it before the reply but this was very clear, cheers
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4evershinee
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(Original post by wag12k12dunkno)
thanks so much! i just did it before the reply but this was very clear, cheers
No probs
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wag12k12dunkno
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(Original post by 4evershinee)
No probs
What mass of calcium chloride would be required to prepare 2 litres of 0.5 M calcium chloride

So do i find out the moles so (2*0.5)/1000= 0.001

so then moles= mass/molar mass
so mass= moles* molar mass

molar mass of cacl2 is 111

so 0.001*111= 0.111

i know iv gone wrong somewhere here
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wag12k12dunkno
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(Original post by Munrot07)
you have a volume and a concentration so work out the moles n = (C x V)/1000

Then work out the mass m = n x Mr (you know that sodium carbonate is Na2CO3 so use the periodic table to work out the Mr)
please help with next question im not sure where i went wrong i dont know if i had to divide by 1000 or not
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cleveradam
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(Original post by wag12k12dunkno)
What mass of calcium chloride would be required to prepare 2 litres of 0.5 M calcium chloride

So do i find out the moles so (2*0.5)/1000= 0.001

so then moles= mass/molar mass
so mass= moles* molar mass

molar mass of cacl2 is 111

so 0.001*111= 0.111

i know iv gone wrong somewhere here
convert L to ML = 2L = 2000ML
2000 X 0.5/1000= 1
1 x 111 = 111

Remember that ml=cm3 they're both the same.
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Munrot07
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(Original post by wag12k12dunkno)
please help with next question im not sure where i went wrong i dont know if i had to divide by 1000 or not
you only divide by 1000 if you have cm^3 because you need it in dm^3. If the volume is in dm^3 do not divide by 1000. 1dm^3 = 1 litre
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wag12k12dunkno
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(Original post by cleveradam)
convert L to ML = 2L = 2000ML
2000 X 0.5/1000= 1
1 x 111 = 111

Remember that ml=cm3 they're both the same.
why do i have to convert L to ML in the last question i just divided by 1000
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wag12k12dunkno
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(Original post by Munrot07)
you only divide by 1000 if you have cm^3 because you need it in dm^3. If the volume is in dm^3 do not divide by 1000. 1dm^3 = 1 litre
ok cheers
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wag12k12dunkno
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(Original post by Munrot07)
you only divide by 1000 if you have cm^3 because you need it in dm^3. If the volume is in dm^3 do not divide by 1000. 1dm^3 = 1 litre
how do i find the number of moles in an element if im given the amount of grams of the element

moles= mass/molar mass dw i was being dumb
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wag12k12dunkno
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(Original post by Munrot07)
you only divide by 1000 if you have cm^3 because you need it in dm^3. If the volume is in dm^3 do not divide by 1000. 1dm^3 = 1 litre
dw i worked it out
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Shantelly
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thanks a lot
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mrcullen
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You need to prepare 2.500 L of 1M sodium carbonate. What mass of sodium carbonate is required for this solution?
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mrcullen
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(Original post by wag12k12dunkno)
thanks so much! i just did it before the reply but this was very clear, cheers
You need to prepare 2.500 L of 1M sodium carbonate. What mass of sodium carbonate is required for this solution?
can u fix this one?
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mrcullen
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(Original post by mrcullen)
You need to prepare 2.500 L of 1M sodium carbonate. What mass of sodium carbonate is required for this solution?
can u fix this one?
I just tried many times and I got incorrect

the mass for Na2CO3. 105.99 g/mol
and I got for my question 264.975 g/mol so could check out for me please ?
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mrcullen
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(Original post by mrcullen)
You need to prepare 2.500 L of 1M sodium carbonate. What mass of sodium carbonate is required for this solution?
can u fix this one?
I just tried many times and I got incorrect

the mass for Na2CO3. 105.99 g/mol
and I got for my question 264.975 g/mol so could check out for me please ?
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