D. Buffer solution Prepare a baking soda solution by dissolving about a teaspoon
ID: 1034588 • Letter: D
Question
D. Buffer solution Prepare a baking soda solution by dissolving about a teaspoon full of baking soda (NaHCO,) into 50 mL of distilled water. Take the pH of the solution and record. Divide the solution into two portions. To one portion, add 2 drops of IM HCI and swirl to mix. To the other, add 2 drops of IM NaOH and mix. Take the pH of each solution with the meter and record. Prepare another two beakers with 25 mL of distilled water in each. To one beaker, add 2 drops of 1M HCI and swirl to mix. To the other, add 2 drops of 1M NaOH and mix. Take the pH of each solution with the meter or pH paper and record. pH value System tested Baking soda solution Distilled water 7.00 Original After HCI addition After NaOH addition Using your results, discuss which solution showed better buffering action. 83Explanation / Answer
Sample in the melting point of a capillary tube have to be packed tightly so that there is no spaces of air in the capillary tube. This space would not allow the sample to reach the bottom of the tube and hence the sample would melt more slowly. This will cause ending point of the melting point to be too high.
Well sometimes it is very hard to state whether the sample is a pure substance or a homogeneous mixture. Homogeneous mixture like rain water, alcohol are very difficult to be seperated by human eyes. The require special process like distillation etc. to be separated. So some may judge them as pure substance.
Some substance have the property to supercool (i.e lowering the temperature of liqiud or gas below its freezing point without it becoming solid), therefore freezing point is not considered a characterisitic property of substance.
Both Urea and trans cinnamic acid have melting point aaround 132-133 degree centigrade. If a substance is contaminated with its pure form then its melting point is reduced. So the mixture has melting point is around 103-109 degree centigrade.
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