# Pls help with chemistry hw- tried to do this for an hour but had no luck. ThanksWatch

Thread starter 2 years ago
#1
Balance the equation;
Ca(OH)2(aq) + Na2Co3(s) = CaCO 3(s) + 2NaOH(aq)
How many moles are there in 25.0g of sodium carbonate?

ii) Calculate th mass of sodium hydroxide the scientist could expect to form if he reacts 25.0 of sodium carbonate with an excess of calcium hydroxide.

B) Scientist only found out he made 10.4 of sodium hydroxide. Calculate the percentage yield of this
0
2 years ago
#2
Did you manage to get any of the answers? Have you got any useful working out for any of the parts?
1
2 years ago
#3
Isn't the equation already balanced? And do you not have answers? But i got (all answers to 3sf btw taking the equation there is)

moles = 0.236 mol
ii) 18.9g
b) 55%

(Original post by Ilikeharrypotter)
Balance the equation;
Ca(OH)2(aq) + Na2Co3(s) = CaCO 3(s) + 2NaOH(aq)
How many moles are there in 25.0g of sodium carbonate?

ii) Calculate th mass of sodium hydroxide the scientist could expect to form if he reacts 25.0 of sodium carbonate with an excess of calcium hydroxide.

B) Scientist only found out he made 10.4 of sodium hydroxide. Calculate the percentage yield of this
0
Thread starter 2 years ago
#4
(Original post by Ismarika)
Isn't the equation already balanced? And do you not have answers? But i got (all answers to 3sf btw taking the equation there is)

moles = 0.236 mol
ii) 18.9g
b) 55%
Can you show the working out pls
0
Thread starter 2 years ago
#5
(Original post by lizardlizard)
Did you manage to get any of the answers? Have you got any useful working out for any of the parts?
Nope but can you show the working out pls so I know how it's done, thanks
0
2 years ago
#6
(Original post by Ilikeharrypotter)
Can you show the working out pls
So basically you know that mass/molar mass gives you moles so the molar mass of Na2Co3 is 106 and when you do mass/molar mass you should get 0.236
ii) this is kinda poorly worded/set out because if its a solution then I don't know why their talking about it in terms of mass but because they have given you the mass, just work out that and if you look at the ratios using stoichiometry, you should multiply it by 2 to get the moles of NaOH due to 1:2 ratio and then using mass/mm again rearrange the equation to give you mass of NaOH. (Just multiply the moles from stoichiometry with the molar mass of NaOH which was 40)
iii) use your mass as the expected yield and work out the % yield.
Would be nice if you could list answers next time
1
2 years ago
#7
Ca(OH)2(aq) + Na2Co3(s) = CaCO 3(s) + 2NaOH(aq)
How many moles are there in 25.0g of sodium carbonate?

n(Na2Co3)=25/(46+12+48)=0.235849056 mol

ii) Calculate th mass of sodium hydroxide the scientist could expect to form if he reacts 25.0 of sodium carbonate with an excess of calcium hydroxide.

m(NaOH)=n*rfm=(2*0.235849056)*(2 3+16+1)=18.86g

B) Scientist only found out he made 10.4 of sodium hydroxide. Calculate the percentage yield of this[/QUOTE]

actual/theoretical

10.4/18.86=55.12%
0
Thread starter 1 year ago
#8
(Original post by lizardlizard)
Did you manage to get any of the answers? Have you got any useful working out for any of the parts?
Sorry mate but my Chemistry notes are destroyed right now- not studying chemistry anymore
0
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