Neco 2022 Chemistry Question 4

Practice essay / theory question 4 from the 2022 Neco Chemistry examination. This question covers mole concept, stoichiometry, empirical formula .

Neco 2022 Chemistry Essay / Theory

Topics: mole concept stoichiometry empirical formula

Question 4 NECO • 2022 • CHEMISTRY • essay

The diagram shows the structure of the hydrated copper(II) tetraammine sulfate complex, [Cu(NH3)4]SO4·H2O.

Question Parts

( a )

Write the empirical formula of the compound and calculate its molar mass (in g·mol\(^{-1}\)).

( b )

A 2.50 g sample of the compound is dissolved in water. Calculate the number of moles of copper present in the sample. Give your answer to three significant figures.

( c )

When excess sodium hydroxide is added, copper(II) hydroxide precipitates according to: [Cu(NH3)4]SO4·H2O + 2 NaOH → Cu(OH)2(s) + 4 NH3 + Na2SO4 + H2O. Calculate the mass of Cu(OH)2 formed from the 2.50 g sample. (Molar mass of Cu(OH)2 = 97.6 g·mol\(^{-1}\)). Give your answer to two decimal places.

( d )

If the same solution is instead treated with excess silver nitrate, the sulfate ion precipitates as silver sulfate: SO4^{2-} + 2 AgNO3 → Ag2SO4(s) + 2 NO3^{-}. Calculate the mass of Ag2SO4 obtained from the original 2.50 g sample. (Molar mass of Ag2SO4 = 311.8 g·mol\(^{-1}\)). Give your answer to two decimal places.

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About This Question

This is Neco 2022 Chemistry Question 4. It is one of the essay questions from the 2022 Neco Chemistry examination.

The question covers mole concept, stoichiometry, empirical formula .

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