Year 12s: what will be the first way you research your future options? >>

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

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

(edited 7 years ago)

Reply 1

lizardlizard

Did you manage to get any of the answers? Have you got any useful working out for any of the parts?

Reply 2

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%

Original post by Ilikeharrypotter

Reply 3

Ilikeharrypotter

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

Reply 4

Ilikeharrypotter

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

Reply 5

Ismarika

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

Reply 6

username3062024

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)*(23+16+1)=18.86g

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

actual/theoretical

10.4/18.86=55.12%

(edited 7 years ago)

Reply 7

Ilikeharrypotter