Chemistry Answers

How many mL of water must be added to 250mL of 0.578 M CaCl2 solution to give a 0.349 M solution?

4. Write two equations to depict the amphitropic nature of water.

(b) define the following: (I) pH and (II) pKa

(c).For a reaction between a weak acids and water as shown, prove that pH =pKa -log [acid/base].

HB(acid) + H₂O = H₃O⁺ + B^-

(d) List the factors that affect the solubility of a substances.

(e) Calculate the solubility in grams per litre of silver sulphide if the K_sp of Ag₂S is 6.3 x 10^-50

4.1 Use electronic factors to explain why methyl carbanion is more stable than tertiary butyl

carbanion.

4.3 Reaction of 2-methyl-1,3-butadiene with bromine yields a mixture of products: 3,4-

dibromo-2-methyl-1-butene (3 %), 3,4-dibromo-3-methyl-1-butene (21 %) and 1,4-

dibromo-2-methyl-2-butene (76 %).

a) Identify all products as either 1,2 or 1,4 adducts.

b) Propose mechanisms for the formation of all 3 products.

c) Explain why 3,4-dibromo-3-methyl-1-butene (21 %) predominates over 3,4-dibromo-2-

methyl-1-butene (3 %).

2.3 Assuming that the nitrogen in enamine is sp2 hybridized, explain why the double bond of

an enamine is more nucleophilic than a typical alkene double bond.

3.2 The reaction of methylpropene with HBr, under radical conditions, gives two

intermediates. Propose a mechanism for the formation of the two products.

3.4 Draw the structure of an antioxidant, Vitamin E free radical and use resonance structures

to account for its stability

1.3 Draw structures of aniline and cyclohexylamine and use appropriate factors to compare

their basicity.

1.4 Explain why AlCl₃ is a stronger Lewis acid than Al(CH₃)₃

Explain using examples how electronic factors (resonance and inductive effects) can be

used to determine acidity and basicity of organic compounds.

Using Henderson hasselbalch equation determine concentration of acid and conjugate base in 0.1M phosphate at ph 6.24

1. In the form of table , select from the the following species acids - base conjugate -pairs indicating which is the acid and which is the base.

H_2, O^2- ,HPO₄^2- ,NH₃,OH ^-,H₂O, H₂PO₄^-,H^-,NH₄⁺

2. (a). Arrange the following hydrated cations in order_by of increasing strength as Bronsted - Lowry acids and account for your sequence .

[Na(H₂O)_x ]⁺, [Al(H₂O)_x]³⁺, [Mg(H₂O)_x]²⁺

(b) Which of the under-listed acids is stronger and why ?

(I) CH₂ClCOOH and (II) CH₂COOH

Determine the volume occupied by 2.5 mol of a gas at 18 degrees if the pressure is at 81.8 kPa

A 5L flask at 25 degrees contains 0.2 mol of Cl2. What is the pressure in the flask?