Help me with this question pretty please ^_^? (1 Viewer)

[Nyo]

A 500mL bottle of concentrated sulfuric acid (18molL-1) was dropped in a laboratory accident. Solid sodium hydrogen carbonate (NaHCO3) was used to neutralize the spilled acid.

a) Justify the choice of the solid sodium hydrogen carbonate to clean up the spill. Include relavent equaltions(s).

b) Calculate the minimum mass of sodium hydrogen carbonate needed to neutralise the spilled acid completely.


Good luck guys!

(HINT: question a is worth 4 marks and question b is worth 3.)

Thanks in advance!

 

[kooltrainer]

too hard

 

[Nyo]

Lol >_< There must be Someone who can help~
-looks out into the far distance-
​

 

[Undermyskin]

I'll just give it a go.

a. Sodium carbonate is an amphiprotic substance which is widely used to neutralize both spilled acids and bases. In this reaction with sulfuric acid, the reaction is as followed:

2NaHCO3(aq) + H2SO4(aq) -> Na2SO4(aq) + 2H2O(l) + 2CO2(g)

All the products of this reaction are harmless: neutral salt, water and carbon dioxide gas. Salt can be washed away easily. Water helps dilute the remaining acid, reducing the damage. Carbon dioxide is non-poinsonous but there is a need to use air-conditioning to ventillate the current.

Sodium bicarbonate itself is rather safe to handle, especially in the form of powder (conventional product). It is not as damaging as some other bases which people think of straight away to neutralize acids. e.g. NaOH is corrosive and able to saponify the fatty acids present on skin. Any excess use of sodium bicarbonate is not of as much concern as other bases.

Moreover, acid-base reaction is exothermic (esp. between a strong base and a strong acid). In this context, sodium bicarbonate (in regards to sulfuric acid) is a weak base. Hence, the heat released of the neutralization doesn't exacerbate the surfacial damage as much.

b. n H2SO4 = 0.5 * 18= 9 mol
--> n NaHCO3= 18 mol
--> m NaHCO3 = 18*(22.99+1.008+12.01+48)= 1512.144g = 1.5 kg (2 sig. fig.)

 

[tommykins]

回复: Help me with this question pretty please ^_^?

A 500mL bottle of concentrated sulfuric acid (18molL-1) was dropped in a laboratory accident. Solid sodium hydrogen carbonate (NaHCO3) was used to neutralize the spilled acid.

a) Justify the choice of the solid sodium hydrogen carbonate to clean up the spill. Include relavent equaltions(s).

b) Calculate the minimum mass of sodium hydrogen carbonate needed to neutralise the spilled acid completely.


Good luck guys!

(HINT: question a is worth 4 marks and question b is worth 3.)

Thanks in advance!

a) Solid Sodium Hydrogen Carbonate is used as it is an amphiprotic substance, that is - according to the Bronsted-Lowry definition, it is able to act as both an acid and base.

Include relevant equations -

Since it's 4 marks, i'd even go to the point to add in NaHCO3 acting as an acid in a spill (use NaOH as an example or something).

b) 2NaHCO3(aq) + H2SO4(aq) -> Na2SO4(aq) + 2H2O(l) + 2CO2(g)
c = n/v

n = cv = 18*0.5 = 9

Since the balanced equation has a 2:1 ratio betweeen NaHCO3 and H2SO4, we need 18 moles of NaHCO3 to neutralise the spill.

m(NaHCO3) = 18*M(NaHCO3) = 18*84g = 1512g = 1.512kg

 

[Nyo]

Re: 回复: Help me with this question pretty please ^_^?

Ah~ Thank you for the help Tommy ^^​

 

[tommykins]

回复: Re: 回复: Help me with this question pretty please ^_^?

A good piece of advice is in exams, look at how much the question is worth and make your own criteria that fits the whole marking scheme (which normally you'd be right).

ie. Discuss ethanol's potential as a raw-material for producing petrochemicals [7]

My criteria would be -
[1] Identify how ethanol is produced/chemical formula
[1] Sources of ethanol and stating renewable source
[4] Advantages and disadvantages of ethanol as a raw-material/replacement
[1] Make a judgement on it's potential (even though it's not assess, 7 marks is a biggie and alot of kids lsoe a mark because they don't discuss it's potential)

1+1+4+1 = 7.