1- A student synthesized NiNH3)nC12 from NiC12. 6H20 using procedures described

Question

1- A student synthesized NiNH3)nC12 from NiC12. 6H20 using procedures described in the lab manual. The student dissolved 0.90g of the product, Ni(NH3)nC12, in 40 mL of 1.0M HCl to make a sample for analysis. Answer the following showing all of your calculations and include units and proper significant figures. Molar masses: Ni: 58.7 g/mol, Cl: 35.5 g/mol, NH3: 17 g/mol. (a) The student created a standard curve in the same way we did in lab and obtained the following graph: the absorbance of his product was 0.0199. Calculate the mass percent of Ni in the product.(10 points) Concentration of Nickel 0.12 y-02x+ 3E-17 0.1 0.08 0.06 004 0.02 0.1 0.2 0.3 0.4 0.5 0.6 concentration, mol/L

Explanation / Answer

1) Absrobance v/s concentration graph gives straight line with equation

y = absrobance = 0.2x + 3 X 10-17

For absrobance = 0.0199

0.0199 = 0.2x + 3 X 10-17

x = concentration = 0.0995 mol / L

the atomic weight of Ni = 58.7 g / mole

Mass of Ni per L = 0.0995 X 58.7 g / L = 5.84g / L

The volume of solution taken = 40mL

so mass of Ni in 40mL = 5.84 X 40 / 1000 = 0.2336 grams

MAss of sample taken = 0.90g

% of Nickel = 0.2336 X 100 / 0.9 = 25.96%

2) Initial volume of HCl taken = 40mL with concentration 1M

Moles of HCl used = Molarity X volume in L = 1 X 20 / 1000 = 0.02 moles

Moles of NaOH used = 0.336 X 25 / 1000 =0.0084

so moles of HCl used in reaction with complex = 0.02 - 0.0084 = 0.01916 moles

Moles of NH3 present = 0.01916 moles

Mass of NH3 present = Moles X mol wt of NH3 = 0.01916 X 17 = 0.32572g

% NH3 = 0.32572 X 100 / 0.9 = 36.19 %

MAss % of Cl = 100 - (36.19 + 25.96) = 37.85

c) Let we have 100 g of complex

Mass of Ni = 25.96

Moles of Ni = 25.96 / 58.7 = 0.44

Moles of NH3 = 36.19 / 17 = 2.13 moles

Moles of Cl = 37.85 / 35.5 = 1.1

converting them in whole number

Moles of Ni = 0.44/0.44 = 1

Moles of NH3 = 2.13/0.44= 4.84

Moles of Cl = 1.1 / 0.44 = 2.5

So formula will be

Ni(NH3)4Cl2

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.