3.786g of hydrated zinc sulphate, ZnSO4•xH2O, is heated to remove all water of crystallisation. The mass of anhydrous ZnSO4 formed is 2.122g. What is the formula of the hydrated zinc sulphate?

Water of crystallisation describes water molecules that are bonded into a crystalline structure of a compound. By knowing the mass of the hydrated salt (3.786g) and of the anhydrous salt (2.122g) it is possible to work out the formula of the hydrated salt. First, write out the chemical equation for the reaction: ZnSO4•xH2O(s) → ZnSO4 (s) + xH2O(l)Next, work out the mass of the water (mass of the hydrated salt-mass of the anhydrous salt): 3.786g-2.122g= 1.664gThen, work out the number of moles of water and of the anhydrous salt using n=m/M: Number of moles of water: 1.664g/18gmol-1= 0.092444molFormula mass of the anhydrous salt: 65.4+32.1+(16x4)= 161.5gmol-1Number of moles of the anhydrous salt: 2.122g/161.5gmol-1 =0.013139molFinally, work out the ratio of the number of moles of water to the number of moles of the anhydrous salt and so X:Ratio: 0.092444mol/0.013139mol= 7.04Therefore X= 7 and the formula of the hydrated salt is ZnSO4•7H2O

Answered by Claire F. Chemistry tutor

7554 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

Molecules of hydrogen chloride, HCl, and molecules of fluorine, F2, contain the same number of electrons. Hydrogen chloride boils at –85 °C and fluorine boils at –188 °C.Explain why there is a difference in the boiling points of HCl and F2.


What is the mechanism for nucleophilic addition reactions at carbonyls?


Write equations and give the mechanism for the reaction of butanone with: 1) NaBH4 and 2) HCN


How do I calculate the percentage by mass of a metal within an impure substance?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2024

Terms & Conditions|Privacy Policy
Cookie Preferences