09 Instrumentation Laboratory

This event is limited to the first 24 entries.

2019 Topic: Ka and Molar Mass of an Unknown Acid Using a pH Probe

OBJECTIVE

To determine the dissociation constant, Ka, and molar mass of a weak monoprotic acid using a pH probe by preparing a pH titration curve of the unknown acid, given only 1 gram total of the unknown.


Materials Provided by NJIT on the Day of the Event

  • 1.0 gram sample of a weak acid
  • 0.10 M NaOH

Materials & Methods Brought by Team to the Competition: 

  • You will only get a 1.0-gram sample (total), therefore you must use methods appropriate to a small scale

  • Bring whatever is needed to perform the experiment (don’t forget the pH probe; electrical outlets are available).

  • Deionized water (make sure the team has brought enough!)

  • Graph paper

  • Prior to starting, each team must provide the judges with a typed step-by-step description of the methods intended to use to address the objective of this experiment.

INSTRUCTORS NOTES ON SPECIAL SAFETY CONSIDERATIONS:

  • Laboratory should be supervised by instructor/coach at all times.  
  • Review all procedures for safety concerns.  
  • Teams will be permitted to perform their experiment only if their procedure is approved by the judges in accordance with safety protocols.
  • Safety protocol must be addressed in the team's procedure submitted for evaluation prior to the event.
  • Teams must practice procedure prior to event day. Judges reserve the right to dismiss unprepared teams the day of the event.


Prior to the event:

A step-by-step Description of the Theory, Methods and Safety Protocol must be received by the NJCO Event Coordinator by the deadline indicated in the Requirement Overview. The procedure should be practiced thoroughly.  Judges may disqualify entrants who are not confident about their procedure and as a result pose a safety risk.  Be familiar with and be prepared to follow all safety guidelines associated with the method chosen.

On the Day of the event:   

  • Follow the submitted laboratory procedure to collect and record data for a minimum of two trials.
  • Draw a graph (bring graph paper) of the titration curve.  Indicate the endpoint on the graph.  Show any relevant calculations.
  • The Ka of the unknown acid should be determined by interpolation of the graph or the linear regression formula.
  • Clean up and then submit the report showing all calculations on the back of the report page.


Time Limit:   75 minutes


JUDGING CRITERIA

  • Description of methods, 30%
  • Description of safety concerns addressed within procedure, 10%
  • Presentation of Data and Calculations, 25%
  • Accuracy of Ka and molar mass,25%
  • Time, 10%


Notes:

  • In the event of a tie, the team that completes this session in the shortest period of time will win the tie.
  • Teams must clean up and remove all materials that they bring to this event and return them to their own schools.  


ALL PARTICIPANTS MUST BRING APPROVED GOGGLES, GLOVES AND APRON OR LAB COAT, AND USE SAFETY EQUIPMENT AT ALL TIMES DURING THE COMPETITION.  STUDENTS MUST ADHERE TO BOTH GENERAL LAB SAFETY PROTOCOLS AND THOSE SPECIFIC TO THEIR CHOSEN PROCEDURE.