Washing soda, a compound used to prepare hard water for washing laundry, is a hydrate, which means that a certain number of water molecules are included in the solid structure. its formula can be written as na₂co₃⋅xh₂o, where x is the number of moles of h₂o per mole of na₂co₃. when a 3.837 −g sample of washing soda is heated at 25 ∘c, all the water of hydration is lost, leaving 1.42 g of na₂co₃.
what is the value of x?

moles H₂O = 10

Explanation:

The mass of Na₂CO₃⋅xH₂O is 3.837 g and the mass of Na₂CO₃ is 1.42g

Therefore the mass of xH₂O is 3.837 - 1.42 = 2.417 g

The molar mass of Na₂CO₃ is 106 g/mol and for H₂O is 18 g/mol

The moles of Na₂CO₃ and H₂O in the sample are:

Na₂CO₃ = 1.42 / 106 = 0.01340 moles

H₂O = 2.417 / 18 = 0.1343

Now using rule of three :

1 mole of Na₂CO₃ has x moles of H₂O

0.01340 moles of Na₂CO₃ has 0.1343 moles of H₂O

x = 1 * 0.1343 / 0.01340 = 10

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.

what are the statements