FORMULA FOR NUMERICAL (IMPS)

BS 4 (ANA CHEM)

IMPORTANT FROMULAES FOR NUMERICALS:

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DILUTION: C_sV_s = C_dV_d

MOLARITY FROM DENSITY & PURITY:  M = (density X purity X 1000) / (mol weight X 100)

AMOUNT FROM MOLARITY: A = molarity X mol mass X vol in dm³

AMOUNT FROM NORMALITY: A = normality X equ weight X vol in dm³

RELATION BETWEEN MOLARITY & NORMALITY: Molarity = n (Normality)

pH & pOH: pH =-log[H⁺], pOH = -log[OH^-], pH + pOH = 14

MOLARITY TO ppm: Molarity = (g/L) X 1000 = _____mg/L (mg/L = ppm)

DISSOCIATION CONSTANT: K_w = K_a X K_b = 1.0X10^-14M

OXIDATION NUMBERS:

ION ELECTRON METHOD FOR BALANCING REDOX EQUATIONS:

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Questions For Practice:

1. calculate the molarity of NaCl prepare by dissolving 10 g in 500ml.

2. A HCl solution has specific gravity 1.77g/ml and 95% by weight.  Calculate its Molarity

3. Calculate the ppm of 0.5M NaCl, 0.1M HCl ?

4. calculate the pH & pOH of 0.1 M HCl?                                                                                               

5. If pH of a solution is 9.2. Calculate concentration of H⁺ and OH^- in solution?

6. calculate the concentration of HCl prepare by diluting 2mL, 2M solution in 20 mL.

7. If The K_b for NH₃ is 1.75 x10^-5 at 25⁰C.Calculate pH and pOH of  1 x10^-3 M of NH₃ solution.

HINT:

Kb = [NH­₄⁺][^-OH] / [NH₃]

Let [NH₄⁺]=[-OH] = x

Kb= x2/[NH₃]

Find x

Therefore [-OH] = x

Than find pH & pOH

8. Balance the following equations by ion electron method.                                                                          

MnO₄^-  + Fe²⁺     -->   Mn²⁺ + Fe³⁺ (basic medium)

MnO₄^- + SO­₃^2- + OH^- --> Mn²⁺  + SO₄^2-

Cr³⁺ + SO₄^2- --> CrO₄^2- + SO­₃^2- (basic medium)

Zn + VO₂ ⁺ +  H⁺  -->   Zn²⁺  +  VO ⁺²

9. Assign the oxidation number of the following ions

 (i)  NiCl₂,      (ii) FeSO₄            (iii) TiO₄^4-,           (iv) MnO₂                 (v) Al₂O_3,     (vi) MnO₄-    (vii) Cr₂O₇^2- (viii) C₂O₄^2-    (ix) PO₄^3-      (x) V₂O₅

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