Question

To determine the solubility of benzoic acid at different temperatures and to determine h of the dissolution process.

Answer 1

Answer:

Answer:-

Solubility of benzoic acid at different temperature is as follows :-

Temperature (95 °C) -> 68 g/L Solubility

Temperature (90 °C) -> 45.5 g/L Solubility

Temperature (0 °C) -> 1.7 g/L Solubility

The solubility of compound is determined by the amount of material dissolved in a certain amount of solvent.

For Benzoic acid, the ph of the water matters. At high pH, the benzoic acid forms a soluble salt hence the solubility increases as the pH increases. At low pH, benzoic acid doesn’t dissolve as much.

Answer 2

Apparatus:  

Beakers, burette, pipette, filter paper, funnel and thermometer ..etc.  

Chemicals:  

Solid benzoic acid, 0.05N NaOH solution and phenolphthalein indicator.  

The process of dissolution of solid into liquid is usually accompanied with the  absorption or evolution of heat.

The heat of solution in the present experiment is  the heat evolved or absorbed when one mole of the solid is dissolved in a solution  which is already saturated. It differs from the heat of a solution at infinite dilution  by an amount equivalent to the heat of dilution from saturation to infinite dilution.  

The effect of temperature on solubility is given by vant Hoff s equation:  

d In S AH  

dT RT 2  

Where, S is solubility (strength) and AH, heat of solution.  

On integration of the above equation, we have  

Theory:  

-AH  

LogS =  2.303 RT  

Where, R = 1.987 cal/mole.  

Procedure:  

1) Prepare the saturated solution of benzoic acid at 45°C, 35°C, 30°C, 25°C,  20°C and 15°C.  

2) By taking 100 ml of distilled water in a beaker. Add increasing amount of  benzoic acid with constant stirring until a small amount of solid remains  

undissolved.  

3) Pipette out 10 ml of saturate solution in a conical flask. To prevent sucking  of small crystal into the pipette along with the solution, a small piece of filter  paper wrapped around the tip of pipette and fastened with thread. The filter  paper should be removed before draining pipette.  

4) Titrate this solution against 0.05N NaOH solution using ph.ph as an  

indicator.  

5) Then determine the normality and strength of benzoic acid.  

Calculation:  

i) Strength = Normality x Equivalent weight  

ii) Plot log S vs 1/T. from the slope of the straight line calculate heat of  

solution AH as  

AH = - 2.303 x R x Slope (cal/mole)

#BAL #answerwithquality