Percent recovery = amount of substance you actually collected / amount of substance you were supposed to collect, as a percent. Let's say you had 10.0g of impure material and after recrystallization you collected 7.0 g of dry pure material. Then your percent recovery is 70% (7/10 x 100).
What is a good percentage yield?
According to Vogel's Textbook of Practical Organic Chemistry, yields around 100% are called quantitative, yields above 90% are called excellent, yields above 80% are very good, yields above 70% are good, yields above 50% are fair, and yields below 40% are called poor.
Part 3 Calculating Percent Yield
- Understand percent yield. The theoretical yield you calculated assumes that everything went perfectly.
- Write down the actual yield of the experiment.
- Divide the actual yield by the theoretical yield.
- Multiply by 100 to convert to a percentage.
Percent recovery computes the percentage of an original substance that is recovered after a chemical reaction is completed. These mainly include purification reactions. It also determines their efficiency. In organic chemistry, some elements are purified by performing the process of recrystallization.
Percent yield is the percent ratio of actual yield to the theoretical yield. It is calculated to be the experimental yield divided by theoretical yield multiplied by 100%. It's possible for percent yield to be over 100%, which means more sample was recovered from a reaction than predicted.
It is an uncommonly simple natural product extraction because nutmeg oil generally consists of over eighty percent trimyristin. Trimyristin makes up between 20-25% of the overall mass of dried, ground nutmeg.
An analyst usually divides the unknown sample into two portions, so that a known amount of the analyte (a spike) can be added to one portion. These two samples, the original and the original plus spike, are then analyzed.
Characteristics of a Good Recrystallization Solvent: 1. The recrystallization solvent should NOT dissolve the substance to be purified at room temperature, but it should dissolve it well at the solvent's boiling point 2. The solvent should dissolve soluble impurities well at room temperature.
Water is capable of dissolving a variety of different substances, which is why it is such a good solvent. And, water is called the "universal solvent" because it dissolves more substances than any other liquid. It is water's chemical composition and physical attributes that make it such an excellent solvent.
Recrystallization is a technique used to purify solid compounds. During recrystallization, an impure solid compound is dissolved in a hot liquid until the solution is saturated, and then the liquid is allowed to cool. 2. The compound should then form relatively pure crystals.
Recrystallization is the process in which deformed grains of the crystal structure are replaced by a new set of stress-free grains that nucleate and grow until all the original grains have been consumed. The process is accomplished by heating the material to temperatures above that of crystallization.
Temperature also affects the growth of crystals because "the higher the temperature, the warmer the crystal solution will be, and the faster its molecules will move. This movement allows them to evaporate more quickly, leaving particles behind to form into crystals.
The simplest and fastest crystals to grow are Epsom salt (magnesium sulfate) crystals.
Warm air temperature aids water evaporation, causing the crystals to grow more quickly. Crystals will still grow in cooler temperatures, but it will take much longer for the water to evaporate. Crystal growth also requires light. Again, the crystals will eventually grow in the dark, but it will take a very long time.
Sugar crystals are called rock candy because these hard crystals are edible. Sugar (sucrose) crystals are one of the few types of crystals you can grow and eat. You can eat the natural clear crystals or you can color and flavor them. Dissolve the sugar in the boiling water.
If you do use a plastic jar/container make sure that it can withstand the heat of boiling water and will not melt/deform. If any of your strands fuse together, gently pull them apart. Borax crystals are pretty hearty.
After dissolution, borax particles will again separate from the water if left sitting for extended periods.
- Measure one cup of hot tap water with a measuring cup.
- Measure one teaspoon of borax with a measuring spoon.
- Stir until all the borax is dissolved in the water.
Hot water holds more borax crystals than cold water. That's because heated water molecules move farther apart, making room for more of the borax crystals to dissolve. When no more of the solution can be dissolved, you have reached saturation. As this solution cools, the water molecules move closer together again.
These polymer molecules slide past each other as a liquid. Borax in water forms an ion called the borate ion. When the borax solution is added to the glue solution, the borate ions help link the long polymer molecules to each other so they cannot move and flow as easily.
Toxicity. Borax, sodium tetraborate decahydrate, according to one study, is not acutely toxic. Its LD 50 (median lethal dose) score is tested at 2.66 g/kg in rats, meaning that a significant dose of the chemical is needed to cause severe symptoms or death. The lethal dose is not necessarily the same for humans.
Boric acid is low in toxicity if eaten or if it contacts skin. However, in the form of borax, it can be corrosive to the eye. Borax can also be irritating to the skin. People who have eaten boric acid have had nausea, vomiting, stomach aches, and diarrhea.
"Borax can cause burns, especially when you touch it multiple times," she says. "Borax is a mild irritant," he says. "I love that kids are having fun with slime, and it is generally safe."