Lab 3

Maleic acid and malonic acid have very similar names, and coincidentally, very similar melting point ranges. Maleic acid melts between 134-136 °C, and malonic acid melts between 135-137 °C. If a student inadvertently returned some malonic acid to the maleic acid jar, which of the following melting point ranges would you expect to find of the maleic acid mixture now?

130-135 C

While directly measuring a melting point in the lab, you should use a setting on the apparatus so that the temperature rises no more than ____ to ___ degrees per minute.

2,3

A student performs a recrystallization similar to how we did it in lab to purify salicylic acid from sodium chloride using warm water as the solvent. After heating the mixture until all of the material dissolves, the solution cools and a white precipitate forms. The student then performs a vaccum filtration to separate the white precipitate from the solution. Where can the student find the sodium chloride? A. Collected in the Büchner funnel B. Dissolved in the water filtrate (the "mother liquor") C. Evaporated D. Vacuumed away into the house vacuum system

B

Which of the following compounds is the most soluble in room temperature water? A) Benzene B) Sodium Benzoate C) Benzoic Acid D) Biphenyl

B

At which of the following temperatures would sodium acetate be MOST soluble in water? A) 0 C B) 22 C C) 50 C D) 90 C

D

Imagine that you are on a camping trip to the Boundary Waters in northern Minnesota. It is a very remote area and there aren't any stores nearby, so you have all of the usual camping items with you-- water, small stove, cooking pot, coffee, coffee filters, bottles, etc. For breakfasts on the trip, you have brought along some multi-grain oatmeal. But, as we all know, that stuff only tastes good with lots of sugar on it. Halfway through your trip, however, your bag of sugar gets a bunch of sand in it. You can't eat the sugar with a bunch of sand in it, but you don't want to eat your oatmeal plain, either. In order to prevent having to go back, how can you purify the sugar and save your trip? Put the following steps in the correct order (1 is first, 2 is second, etc). A. Continue to heat the mixture and add water until all the sugar dissolves. B. Add some water to the solid mixture. C. Keep the solution you filtered and allow the water to evaporate, leaving you with solid, purified sugar. D. Heat the mixture on the camp stove. E. Dump your sugar/sand mixture into the coffee pot. F. Pour the hot solution through a coffee filter, which removes the insoluble sand from the sugar/water solution.

E,B,D,A,F,C

In the lab, melting points are measured as single temperature values. TRUE OR FALSE HABIBIE?

False

In this lab, you will be using a ________ apparatus to measure melting point ranges.

Mel-Temp

The impure benzoic acid sample we will use in lab contains which of the following components?

benzoic, sodium acetate

To perform a melting point determination, a small amount of powdered sample is placed inside a melting point __________ tube.

capillary

Impure samples have melting point ranges that are both __________ and ____________ compared to a pure sample.

depressed, broadened

The phenomenon of melting point depression is used in every-day life during the winter whenever roads are salted. Ice and salt are mixed together to lower the melting point of water, making roads less slippery until colder temperatures. The precise composition of salt and ice to yield the lowest melting point temperature is with 23 wt% salt. This value is called the _______ point for a mixture.

eutectic

If you mix compound A (melting point range: 43-44 °C) with compound B (melting point range: 44-45 °C), then you will observe the mixture to have a melting point range of 43-45 °C. TRUE OR FALSE (i ran out of ideas lol sorry)

false

The faster one performs a melting point determination, the _____ the melting point range will be.

less accurate

Crushing a solid compound into a fine powder results in a _____ melting point range than melting one large crystal.

more accurate

Because the presence of impurities lowers the melting point, the melting point can be a good indicator of purity: the _________ the material, the ________ its melting point, and the __________ the melting point range.

purer,higher,narrower

Melting points are always measured as a ________

range

What physical property of organic compounds does recrystallization exploit to achieve purification?

solubility

Crystals grow from _________ solutions.

supersaturated

Impurities should be more soluble in the solvent than the desired material. TrUe Or FaLsE

true

What is the step we will use to physically separate and collect the recrystallized benzoic acid?

vacuum filtration