[kyred]

A sample of 27.8230 g of Na2CO3.kH20 (k is a constant) crystal was dissolved in H2O and made up to 1 dm3.
25.0 cm3 of the solution were neutralized by 48.8 cm3 of 0.1 mol/dm3 HCL.
Find k.
Do I include the kH2O in the equation?
What's the balanced equation?
Do I use MV/1000 (if the V is in cm3)?
How about n=mass/atomic mass?

[Borek]

What's the balanced equation?

That's your main question. What is reacting with strong acid during titration? Number of moles of what substance can you determine this way?

[kyred]

I want to find k.
The Na2CO3.kH2O is reacting with the acid.

[Bo_2Q]

 Na2CO3 + HCl ---> NaHCO3 + HCl

 Then NaHCO3 + HCl ---> NaCl +H2O +CO2 

Add two Chemical equations : Na2CO3 + 2HCl --> 2NaCl + H2O +CO2
  k=10  Na2CO3.10H2O 

 

[kyred]

How do you get k? Detailed steps?

[Borek]

I want to find k.
The Na2CO3.kH2O is reacting with the acid.

As Bo_2Q already suggested - water doesn't react with hydrochloric acid, only carbonate does. You can use this information to find number of moles of carbonate in the sample - this will give you carbonate mass. This in turn will tell you how much water was in the sample - convert it to moles and check, how many moles of water per mole of carbonate.