An experiment

[cockydude]

This is a follow up question following a chemistry practical i did earlier.

M (which is identified as Sodium) formas a compound MHCO3 which decomposes on heating according to the following equation

 

2MHCO3---> M2CO3 + CO2 +H2O

 

given a sample and the usual apparatus found in a school lab. Suggest an experiment which could be used to find the Mr of M.

include (a) diagrams (:D measurements taken © how results could be used to obtain Mr of M

 

Help is much appreciated

[Mercedes Benzene]

Suggest an experiment which could be used to find the Mr of M.

 

What is "Mr"??

[Jay-qu]

for the sake of the task why do you refer to M instead of Na..

 

Mr - molar ratio? Relative molecular mass?

[Mercedes Benzene]

for the sake of the task why do you refer to M instead of Na..

 

Mr - molar ratio? Relative molecular mass?

 

I know. I was confused all over...

[cockydude]

Sorry guys Mr is relative molecular mass

[ronthepon]

Here is the basic procedure I can conjure up.

 

1- Take.. um... 100 grams of [math]NaHCO_3[/math].

 

2- Put it in a flask, and on the top, make a pipe arrangement (preferrably from glass) that allows evolved gases to move only though it.

 

3- Now lead the pipe into U- shaped tubes. Have the U-tubes filled with [math]KOH[/math] and anhydrous [math]CaCl_2[/math].

 

4- Now perform the heating reaction... Make sure the gases emanating pass through the [math]KOH[/math] and [math]CaCl_2[/math].

 

5- The change in weight of the [math]KOH[/math] shows the mass of [math]CO_2[/math] that has come out and that of [math]CaCl_2[math] will tell you how much water has come out.

 

Using this method, you can measure the masses of the products. Now, what you must do is calculate from the mass, the number of moles of water and CO2 evolved.

 

And, For every mole of water, you can say that twice the number of moles of [math]NaHCO_3[/math] were originally present.

 

Now, you'll know the 'Mr' of [math]NaHCO_3[/math], so you can easily find out the Mr of Na. Incase you're not sure how,

 

'Mr of Na' = Mr of NaHCO3 - (Mr of H + Mr of C + 3(Mr of O))

 

Incase you have some doubt about what I suggested, go on to clear it with the rest of the hypographers!

 

Good luck.