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

shield volcanos are angry and get mad over the smallest things so much that there heads erupt   pahoehoe and a'a lava. a composite volcano is the poller opposite of a shield volcano. its   peaceful thing and knows how to control its emotions.      

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.