• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

What is the unknown white powder?

Extracts from this document...

Introduction

Neerav Shah IB Chemistry Qualitative Analysis Lab January 31, 2003 Problem: What is the unknown white poweder? (glucose, sodium chloride, sodium tetraborate, calcium chloride) Hypothesis: I think that the unknown substance is sodium tetraborate (borax). Background: Calcium chloride - stable reactivity / white colorless crystals / granules / irritant to body tissue / "not all health aspects have been fully investigated" / density = 0.835 / very soluble in alcohol Sodium Tetraborate (borax) - white, odorless crystals / powder / stable reactivity / density = 1.73 / "not all health aspects have been fully investigated" / melting point = 75 degrees Celsius / insoluble in alcohol / pH = 9.5 , 1g/16mL of water Sodium chloride - density = 2.17 / 1g/2.8mL of water / slightly soluble in alochol / pH = 7 / colorless / transparent / crystals / stable reactivity / "not all health aspects have been fully investigated" / slightly toxic Glucose - melting point = 83 degrees Celsius / 1g/1mL og water / ...read more.

Middle

* Compare the unknown with the rest of the substances * Next, using the formula d = g/L, calculate and record the density of each substance * Using the pH strips, figure out and record the pH of each substance and compare it with the unknown substance *To calculate the density of the unknown substance, a 1 molar solution of the unknown substance was given to us. This solution was used to calculate the pH and the conductivity of the unknown substance. We then evaporated the water to calculate the amount, in grams, of the unknown substance in 50mL of water. We could then use that to calculate density. Data: Grams: Calcium Chloride --> [ (110.98g) / (1 mol) ] (.05 moles) = 5.55g Sodium Tetraborate --> [ (381.42g) / (1 mol) ] (.05 moles) = 19.07g Sodium Chloride --> [ (58.44g) / (1 mol) ] (.05 moles) ...read more.

Conclusion

The final piece of data that reinforced this conclusion was that the conductivity of the sodium tetraborate (22 blinks) was closest to that of the unknown substance (19 blinks). Error was abundant in this experiment. However, it did not affect the final conclusion. Firstly, the unknown substance was hot when the indicator was put in. This could have altered the number of blinks that resulted. Also, any of the unknown substance that was stuck to the side of the beaker after evaporation could not be weighed. This probably resulted in a decreased actual mass. To correct these various sources of error, the following could be done: first, wait for the unknown substance to cool before taking any tests. This will avoid any variations in actual data that could have resulted from heat. To remove the second source of error, instead of weighing the substance itself, weigh an empty beaker, and then weigh the unknown substance inside the beaker, and finally subtract the mass of the beaker from the total mass. This will avoid any error in relation to substance stuck to the side. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Aqueous Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Aqueous Chemistry essays

  1. How much Iron (II) in 100 grams of Spinach Oleracea?

    Although my preliminary experiment to show this did not work, I knew from other experiments and text books that this was needed for the reaction to occur. As the volume of Sulphuric Acid (aq) added to the Iron (II)

  2. ‘The Relative Strength of an Unknown Acid’.

    This first titration is described as a rough titration and is used as a guide for the rest of the titrations. All equipment can be used again, the conical flask will be washed out with distilled water, and the burette may need to be topped up.

  1. Identification of an organic unknown.

    not breathe vapour � In case of contact with eyes, rinse immediately with plenty of water and seek medical advice � Take precautionary measures against static discharges. Carboxylic acid (formic acid) � Causes severe burns � Do not breathe vapour � In case of contact with eyes, rinse immediately with

  2. metal extraction and reactivity

    * Oiling/greasing: oil prevents contact with air or moisture * Coating with plastic: prevents steel structure from rusting * Plating: tin coating and chromium plating * Galvanizing: it involves dipping the object into molten zinc. The thin layer of the more reactive Zn metal coating the steel object slowly corrodes and loses electrons to the iron.

  1. Identification of an Organic Unknown.

    This is known as halogenation 6 Primary Alcohol Oxidation Turns from orange to green The dichromate ions are reduced to a green solution containing chromium ions and the primary alcohol undergoes oxidation and aldehyde is formed. Hypotheses 7 Tertiary Alcohol Effervescence, white fumes given off Tertiary alcohol must be present

  2. Identification of Unknown OrganicCompound

    Add 10 drops of H2SO4 and the warm gently. Pour mixture into 400ml beaker containing 200ml water. A Sweet smell is given off Alcohols present, could be primary or Tertiary. The Alchohol was oxidised to and ester. 3 Test for Primary Alchohols using Jones's reagent (CrO3-H2SO4 in H2O)

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work