You have 1.00g sample of hydrate of Na2CO3. By heating the compound, you drive o

Question

You have 1.00g sample of hydrate of Na2CO3. By heating the compound, you drive off the water and are left with 0.3704g of the anhydrous compound.

a. What mass of water has been driven off?

b. What is the % by mass of Na2CO3 in the hydrate?

c. What is the % by mass of water in the hydrate?

d. If you had started with 1.623g of the hydrate, what mass of water would you expect to lose upon heating.

I think for the first part you would just subtract the 0.3704g from the 1g (?)

Not sure about the second or third parts

For the fourth part do you multiply the 1.623g by the answer from part c?

I would prefer to know how to get to the answers rather than be given them.

Thanks for any help

Explanation / Answer

Na2CO3.xH2O (hydrate) => Na2CO3 (anhydrous compound) + x H2O (water)


(a) Mass of water = mass of hydrate - mass of anhydrous compound

= 1.00 - 0.3704 = 0.6296 g


(b) Mass% of Na2CO3 = mass of anhydrous compound/mass of hydrate x 100%

= 0.3704/1.00 x 100 = 37.04%


(c) Mass% of water = mass of water/mass of hydrate x 100%

= 0.6296/100 x 100 = 62.96%


(d) Mass of water lost by 1.00 g of hydrate = 0.6296 g

Mass of water lost by 1.623 g of hydrate = 1.623/1.00 x 0.6296

= 1.022 g

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