Washing soda is a hydrate of sodium carbonate. its formula is na2co3. x h2o. a 2.714 g sample of washing soda is heated until a constant mass of 1.006 g of na2co3 is reached. what is x ?

1.006 g of Na2CO3 is left; which means that (2.714 -1.006) g of water are lost from the hydrated sodium carbonate

So, water present = (2.714 -1.006) = 1.708 g.

Molecular Wt. of water is =18 g
so moles  = 1.708/18 moles = 0.095 moles. 

Now, Na2CO3 has molecular wt. of = 23x2 + 12 +3x16 = 106 g,

so moles of Na2CO3 =  1.006/106 moles = 0.0095 moles 

Ratio is = 0.0095 / 0.095 = 1 / 10    [ moles of Na2CO3 / moles of H2O ]

Ratio is saying on every 1 mole of Na2CO3 , there are 10 moles of H2O

so x is 10

Answer : option c) heat is released during the process.explanation :

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.