SOTIK DISTRICT CHEMISTRY PRACTICAL QUESTIONS

SOTIK DISTRICT CHEMISTRY PRACTICAL QUESTIONS

CONFIDENTIAL

1.  You are provides with;

• Solution M (HCl)
• Solution N (0.1M NaOH)
• Solution P prepared by dissolving 14.3g/dm³ of Na₂CO_3.
  x H₂O.
• Phenolphthalein inidicator
• Methyl orange indicator

You are required to:

1. Standardize HCl solution M

(b) Determine the value of X in Na₂CO₃. XH₂O

Procedure I

Fill the burette with HCl solution M. pipette 25cm³ of NaOH solution N into a conical flask.

Add 2 drops of phenolphthalein indicator and titrate until you obtain a permanent colour change. Record your results in table I below. Repeat the titration two more times and complete the table.

Table 1

(i) What is the average volume of solution M used

(ii) Calculate the number of solution N used  

 (iii) Write the equation for the reaction that took place

 (iv) Calculate the number of moles of solution M in the titre volume

 (v) Find the concentration of solution M in moles per litre

(vi) Calculate the concentration of solution M in grams per litre  

Procedure II

Fill the burette with HCL solution M. pipette 25cm³ of solution P into a conical flask.

 Add 2 drops of methyl orange indicator and titrate against solution M. repeat the titration

two more times and complete the table.

Table II

 (a) What is the average volume of solution M used?

 (b) Calculate the moles of HCl in the titre volume of solution M  

 (c) Write the equation for the reaction that took place

 (d) Calculate the moles of solution P used  

 (e) Find the concentration of Na₂CO₃. XCH₂O in solution P in moles per litre

  (f) State the concentration of Na₂CO₃.XH₂O in solution P in grammes per litre

  (g) Find the R.F.M of Na₂CO₃.XH₂O  

 (h) The value of X in Na₂CO₃. XH₂O

2.  You are provided with;

– 1.0M potassium iodide

– 1.0M lead (II) nitrate

 You are required to use the two to determine the height of precipitate and the volume

of Pb(NO₃)₂ solution used.

Procedure

• Take six test-tubes of equal volume and label them 1to 4
• Run 5cm³ of 1.0M Potassium iodide solution from a burette into each one of them.
• Add 1.0cm³ of 1.0M Lead (II) nitrate solution to the test-tube labeled 1and stir the mixture well with a glass rod.
• Add about 5 drops of ethanol to the mixture, stir and place it in test-tube rack.
• Add 1.5cm³, 2.0cm³, 2.5cm³, 3.0cm³ and 3.5cm³ of the 1.0M lead (II) nitrate to the test-tubes labeled 2, 3, 4, 5 and 6 respectively.  
• Add about 5 drops of ethanol to each test-tube, stir and allow to settle
• Measure the height of the precipitate in each tube in (mm) and record the measurements in the table below:

  (a) Plot a graph of the heights of the precipitate against the volume of lead (II) nitrate

solution added  

(b) Calculate the;

  (i) Number of moles of KI in 5cm³ of 1.0MKI solution

  (ii) Number of moles of Pb(NO₃)₂ solution which reacted completely with 5.0cm³ of 1.0M KI

 (c) How many moles of KI would react with one mole of lead (II) nitrate?

 (d) Write a balanced chemical equations or the reaction between lead (II) nitrate and

potassium iodide  

 (e) Give the ionic equation for the reactions  

(f) What was the purpose of adding ethanol to the mixture?