Use the References to access important values if needed for this question It is

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Use the References to access important values if needed for this question It is often possible to change a hydrate into an anhydrous compound by heating it to drive off the water (dehydration) anhydrous salt A 48.90 gram sample of a hydrate of Na2CrO4 was heated thoroughly in a porcelain crucible, until its weight remained constant. After heating. 23.15 grams of the anhydrous compound remained. What is the formula of the hydrate? hydrated salt Use a period instead of a dot in the formula of the hydrate Submit Answer Try Another Version 9 item attempts remaining

Explanation / Answer

mass of H2O = mass of hydrated salt - mass of anhydrous salt

mass of H2O = 48.90 g - 23.15 g

mass of H2O = 25.75 g

Molar mass of H2O,

MM = 2*MM(H) + 1*MM(O)

= 2*1.008 + 1*16.0

= 18.016 g/mol

mass(H2O)= 25.75 g

use:

number of mol of H2O,

n = mass of H2O/molar mass of H2O

=(25.75 g)/(18.02 g/mol)

= 1.429 mol

Molar mass of Na2CrO4,

MM = 2*MM(Na) + 1*MM(Cr) + 4*MM(O)

= 2*22.99 + 1*52.0 + 4*16.0

= 161.98 g/mol

mass(Na2CrO4)= 23.15 g

use:

number of mol of Na2CrO4,

n = mass of Na2CrO4/molar mass of Na2CrO4

=(23.15 g)/(1.62*10^2 g/mol)

= 0.1429 mol

use:

X = mol (H2O)/mol (Na2CrO4)

X = 1.429 / 0.1429

X = 10

Answer: Na2CrO4.10H2O

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