50cm^3 of Dilute HCl was added to excess CaCO3.
CaCO3 + 2HCl = CaCl2 + H2O + CO2
Total Volume of Gas collected was 500cm^3
Calculate the concentration, in mol/dm^3 of hydorchloric acid.
Could anyone help me?
CaCO3 + 2HCl = CaCl2 + H2O + CO2
Total volume of CO2 = 500 cm^3 = 0.5 dm^3
Number of moles of CO2 = Volume/Molar Volume = ?? (molar volume of gases at r.t.p. = 24 dm^3)
Number of moles of HCl = Comparing mole ratio with CO2 = ??
Concentration of HCl = Mole/Volume = ??
If you have any problems in the steps, feel free to ask.
Originally posted by Garrick_3658:CaCO3 + 2HCl = CaCl2 + H2O + CO2
Total volume of CO2 = 500 cm^3 = 0.5 dm^3
Number of moles of CO2 = Volume/Molar Volume = ?? (molar volume of gases at r.t.p. = 24 dm^3)
Number of moles of HCl = Comparing mole ratio with CO2 = ??
Concentration of HCl = Mole/Volume = ??
If you have any problems in the steps, feel free to ask.
but i didn't miss out n anything that might prevent me from getting the answer rite?
or could u just write the answer? Let me understand how its being done like providing an example or something
What's the difference between volume and molar volume?
Originally posted by NerdzRulz:but i didn't miss out n anything that might prevent me from getting the answer rite?
or could u just write the answer? Let me understand how its being done like providing an example or something
What's the difference between volume and molar volume?
Garrick is doing a fine job trying to help you out.
>>> What's the difference between volume and molar volume? <<<
It should be "sample volume" vs "molar volume". Molar volume = volume of one mole (of the gas), just as molar mass = mass of one mole (of the substance).
No of moles = sample mass / molar mass
No of moles = sample volume / molar volume
Both are obviously true, so use whichever formula is applicable.
If you can't understand why they're true, let's use a Primary school maths example.
If one chicken's mass is 1kg, and I have a sample of an unknown number of chickens, and the sample mass is 10kg, how many chickens do I have in the sample?
No of chickens = sample mass / chicken mass.
Similarly,
No of moles = sample mass / molar mass
Bet your school didn't teach you that way. They just told you to memorize blindly, moles = mass / Mr, which doesn't make sense to most students. No of moles = sample mass / molar mass, on the other hand, makes perfect sense to everybody.
That's why if you (anyone from Sec 3 to JC2) have difficulty understanding Chemistry taught in school, consider coming for my tuition for your own sake.
As for your original problem, let x be the molarity of HCl(aq).
(((50/1000)(x))/(2)) x (24000) = 500
Solve for x, and you've answered the question.
Explanation :
- the 50/1000 is volume in dm3
- the (x) is molarity
- hence (50/100)(x) = no of moles
- the / 2, is due to stoichiometry (ie. looking at the balanced chemical equation).
- hence after dividing by 2, you obtain no of moles of the gas
- the x 24000 is to obtain the sample volume of gas in cm3
- equate it to 500 since that's what's give in the question.
- solve for x, which is molarity (ie. concentration in mol/dm3) of HCl(aq)
tt's the trouble with teaching nowadays... the teachers noe their stuff but dunno how to teach, so just say "memorise blindly"
Originally posted by Garrick_3658:CaCO3 + 2HCl = CaCl2 + H2O + CO2
Total volume of CO2 = 500 cm^3 = 0.5 dm^3
Number of moles of CO2 = Volume/Molar Volume = 0.5/24 = 0.020833 mol (molar volume of gases at r.t.p. = 24 dm^3)
Number of moles of HCl = Comparing mole ratio with CO2 = 0.020833 x 2 = 0.041666 mol
Concentration of HCl = Mole/Volume = 0.041666/0.05(in dm^3 note, since qns wants molarity in mol/dm^3) = 0.833 mol/dm^3
If you have any problems in the steps, feel free to ask.
Quoting myself ftw.