To measure the amount of nickel in some industrial waste fluid, an analytical ch

Question

To measure the amount of nickel in some industrial waste fluid, an analytical chemist adds 0.110 M sodium hydroxide (NaOH) solution to a 25.0 g sample of the fluid and collects the solid nickel(I) hydroxide (Ni (OH2) product. When no more Ni(OH)2 is produced, he filters, washes and weighs it, and finds that 343. mg has been produced The balanced chemical equation for the reaction is: Ni2+(aq) + 2NaOH(aq) Ni(OH)2(s) + 2 Na. (ag) R precipitation | | o acid-base o redox Og Dx10 Ar What kind of reaction is this? If you said this was a precipitation reaction, enter the chemical formula of the precipitate. If you said this was an acid-base reaction, enter the chemical formula of the reactant that is acting as the base. If you said this was a redox reaction, enter the chemical symbol of the element that is oxidized. Calculate the mass percent of Ni in the sample. Be sure your answer has the correct number of significant digits.

Explanation / Answer

1)

This is precipitation reaction as solid is formed in the product

2)

Ni(OH)2 is precipitate

3)

not applicable

4)

not applicable

5)

Molar mass of Ni(OH)2,

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

= 1*58.69 + 2*16.0 + 2*1.008

= 92.706 g/mol

mass of Ni(OH)2 = 0.343 g

mol of Ni(OH)2 = (mass)/(molar mass)

= 0.343/92.706

= 0.00370 mol

According to balanced equation

mol of Ni reacted = moles of Ni(OH)2

= 0.00370 mol

Molar mass of Ni = 58.69 g/mol

mass of Ni = number of mol * molar mass

= 0.0037*58.69

= 0.217 g

This is mass of Ni in original sample

mass % of Ni = mass of Ni * 100 / mass of sample

= 0.217*100/25.0

= 0.868 %

Answer: 0.868 %

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