i suck at chem (please help :3)

[physics]

0.148g of a metal carbonate exactly reacts with 20ml of 0.1M HCl. The formula of the metal carbonate is most likely to be
A. Li2CO3   B. Na2CO3   C.MgCO3   D. Sr CO3

i got A the ans is D
i did
n=0.02 *0.1 =0.002mol
M =m/n and that gives me 74 and ....now i have lost myselfdone!  

SHortened this question below to important bits
There are 2 samples of CaCO3 both weighing 2g. Sample 1 has large pieces of CaCO3 and sample 2 has smaller pieces.
100ml of 0.5M HCl is added to sample 1 and at 18C
equation : CaCO3 + 2HCl--> CaCl2 + H20 +CO2

First question asks for the amount in excess of Hcl which is 0.47684L (used pV=nRT)
then calculate the total change in mass recorded by the balance when all the calcium carbonate has been used up? hate this!grrr iget it now


Why would copper wire be unsuitable for use in flame tests?

When electrons are excited they lose eneergy by jumping from teh shell they are in to a lower energy shell. Examine the spectrum of calcium (there is a bunch of pink lines on one end and another set of violet lines on the other). Which line represents the electron jump of the largest energy? Explain.
I said that the violet light represents the electron jump witht the largest energy.

[happyhappyland]

0.148g of a metal carbonate exactly reacts with 20ml of 0.1M HCl. The formula of the metal carbonate is most likely to be
A. Li2CO3   B. Na2CO3   C.MgCO3   D. Sr CO3

0.1M hcl X 0.02 = 0.002 mol

0.002mol = 0.148/x

0.148/0.002=74molar mass

But you must remember that you dont know the BALANCE equation. Some may work it out by predicting the balanced equation but I would just assume the ratio would be either 1:2 2:1 2:3 or 3:2.
Since the molar mass of CO3 is already 60 I would assume that it may be a 2:1 ratio. So 74X2=148.
148-60=88 Sr is 87.
Otherwise you say
xC03 + 2HCL = Co2 +h2o +xCL2 which is a standard metal carbonate and HCL reaction.


Dont really understand your second question... and the third I just cant do xD

[physics]

0.148g of a metal carbonate exactly reacts with 20ml of 0.1M HCl. The formula of the metal carbonate is most likely to be
A. Li2CO3   B. Na2CO3   C.MgCO3   D. Sr CO3

0.1M hcl X 0.02 = 0.002 mol

0.002mol = 0.148/x

0.148/0.002=74molar mass

But you must remember that you dont know the BALANCE equation. Some may work it out by predicting the balanced equation but I would just assume the ratio would be either 1:2 2:1 2:3 or 3:2.
Since the molar mass of CO3 is already 60 I would assume that it may be a 2:1 ratio. So 74X2=148.
148-60=88 Sr is 87.
Otherwise you say
xC03 + 2HCL = Co2 +h2o +xCL2 which is a standard metal carbonate and HCL reaction.


Dont really understand your second question... and the third I just cant do xD

i got i got it yay! thanks +1

[moneran]

question two  
work out amount of mols of HCL which is 0.1 * 0.5 which is 0.05 mols minus the amount of mols need for cacO3 which is 0.01998 (i usally leave in cas so i have all significant figures) then we know that 2mols of hcl reacts with 1 of the calcium carbonate so divide by 2 which gives 0.05/2= 0.025mols minus 0.01998 which gives 5.02*10^-3  mols of HC in excess, the next part isnt too clear sounds like its a change in mass in the equation but mass can not be destroyed so i must be looking at it wrong, just clarfy if you can

[physics]

question two 
work out amount of mols of HCL which is 0.1 * 0.5 which is 0.05 mols minus the amount of mols need for cacO3 which is 0.01998 (i usally leave in cas so i have all significant figures) then we know that 2mols of hcl reacts with 1 of the calcium carbonate so divide by 2 which gives 0.05/2= 0.025mols minus 0.01998 which gives 5.02*10^-3  mols of HC in excess, the next part isnt too clear sounds like its a change in mass in the equation but mass can not be destroyed so i must be looking at it wrong, just clarfy if you can

kinda f-ed up question

[fady_22]

Copper wire cannot be used because it would produce its own colour which may mask the colour produced by the element being tested.

Violet light has the greatest energy in the EM spectrum, and so you are right.

[physics]

Copper wire cannot be used because it would produce its own colour which may mask the colour produced by the element being tested.

Violet light has the greatest energy in the EM spectrum, and so you are right.

ohhh i think the wording was bad for the copper wire b/c i thought it meant that the copper wire was used in the flame test instead of the copper metal so i got confused

[moneran]

i was getting to the copper part ... lol coulda given me a few mins fady ... had to get onto the laptp and off my iphone lol

[fady_22]

2) The only thing that is lost is the Carbon dioxide (leaves as gas). If you can calculate the mass of CO2 produced using the number of mole of CaCo3, you will find the change in mass.