9. What are the various types of redox reactions presenel in las? Provide an exa

Question

9. What are the various types of redox reactions presenel in las? Provide an example of each. class? Provide an example of A. Combination reactions B. Decomposition reactions C. Combustion reactions D. Displacement reactions 10. What is the SI unit for concentration? What is the equation that accounts for dilution factor? Le. Ratio of old vs new concentration. M,K = M,V, 11. What is the purpose of gravimetric analysis? 12. What is the purpose of an acid/base titration? What is the equivalence point? Some example questions: In a titration experiment, a student finds that 23.48 mL of a NaOH solution are needed to neutralize 0.5468 g KHP. What is the concentration (in molarity) of the NaOH solution? How many milliliters (mL) of a 0.610 M NaOH solution are needed to neutralize 20.0 mL of a 0.245 M H2S04 solution?

Explanation / Answer

Ans 1) The various types of redox reaction are as follows:-

a) Combination reaction :- Those reaction in which two or more than two substances combine to form a single substance is called combination reaction.

2Mg + O2 -> 2MgO

b) Decomposition reaction :- Those reaction in which a compound splits up into two or more simple substances are known as decomposition reaction.

CaCO3 -> CaO + CO2

c) Combustion reaction :- The reaction in which the compound is burned in presence of oxygen is called combustion reaction

CH4 + 2O2 -> CO2 + 2H2O

d) Displacemeent reaction;- Those reaction in which one element takes the place of another element in a compound are known as displacement reaction .

CuSO4 + Zn -> ZnSO4 + Cu

Ans 2) We know

Concentration = Number of moles / Volume (in L)

                      = mol/L

therefore SI unit for concentration = mol/L

Equation for dilution factor = final volume / initial volume

Ans3) The main purpose of gravimetric analysis is to use the chemical formula and mass of precipitate obtained from the experiment to determine the amount of unknown ion.

Ans 4) The main purpose of acid base titration is to find out the amount or concentration of a known acid or base through acid base titration.

The point at which the reaction is complete is known as equivalence point.

Ans 5) a) Given

mass of KHP = 0.5468g

Molar mass of KHP = 204.2g

The reaction between KHP (potassium hydrogen phthalate KHC8H4O4) and NaOH (sodium hydroxide) is as follows;-

NaOH (aq) + KHC8H4O4 (aq) -> KNaC8H4O4 (aq) + H2O (l)

Moles of KHP = Given mass / molar mass

                     = 0.5468 / 204.2

                      =0.00267mol

From the above reaction we can see that 1 mol of KHP neutralizes 1 mol of NaOH

therefore , mole of NaOH = 0.00267

Given , volume of NaOH to neutralize the given number of moles = 23.48ml

Now, molarity of NaOH = (moles of NaOH / Volume in ml) x1000

                                  =(0.00267 / 23.48) x 1000

                                    = 0.11404M

Ans b) Given molarity of H2SO4 = 0.245M

Volume of H2SO4 = 20 ml

Moles of H2SO4 = 0.245x20 /1000

                         = 0.0049mol

the reaction between NaOH and H2SO4 is :-

H2SO4 + 2NaOH -> Na2SO4 + 2H2O

from the above reaction we can see that 1 mole of H2SO4 neutralizes 2moles of NaOH

Therefore moles of NaOH = 2 x 0.0049 = 0.0098 mol

Given, molarity of NaOH = 0.610M

Now, volume of NaOH = moles of NaOH / Molarity of NaOH

                                 = 0.0098 / 0.610

= 0.01606L

Now, we know 1L=1000ml

0.01606L= 0.01606 x 1000

   = 16.06 ml

Therefore volume of NaOH = 16.06 ml   

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