Disadvantages Of Refractometer

Purpose: To learn about the international system of units (SI), to become familiar with common lab equipment and techniques, to gain proficiency in determining volume, mass, length, and temperature of a variety of items using common laboratory measurement devices, to learn to combine units to determine density and concentration, and to use laboratory equipment to create serial dilutions and determine the density and concentration of each dilution.

Spectroscopy is the study of light. A spectrophotometer is a machine used to determine the absorbance of light at any given wavelength. It does this by using a source of white light through a prism, which gives multiple wavelengths that can be individually focused (Ayyagari and Nigam, 2007). Substances are put into cuvettes that are glass or quartz containers that light can easily travel through. The light that is being focused travels through the substance gets absorbed by the

I will be doing this experiment to understand density of water compared to the volume of an object. D=m/v=mass/volume

Temperature is known as one of the factors that affect the solubility of a gas in its solvent. Because the enthalpy of solution for gases dissolved in waters is usually

10 microliters of the sample is then added and the assay absorption is measured at 340nm. If absorbance was above 1.5, samples were diluted.

The main focus of this lab was to measure different tonicities. Tonicity is the concentration of the solute particle mixed with the solvent inside the cell versus said the concentration of solute and solvent outside the cell (Mader 50). There are three different types of tonicity measurements. One type of tonicity is called isotonic. This means that the solution has an equal concentration of solute and solvent both outside and inside the cell (Mader 50). This means that the concentration is in an equilibrium. The second tonicity is called hypertonic. This type of solution has less free water outside of the cell and a higher concentration of the solute particle. Water exits the cell in order to balance the concentration inside and outside the

In the third stage of this experiment, the density of a liquid was determined and compared to known standards. A 100ml beaker was filled to about half-full with room-temperature distilled water. The temperature of the water in ◦C was recorded in order to compare to known standards later. A 50ml beaker was then weighed on a scale in order to determine mass and recorded. A sample of the distilled water with an exact volume of 10ml was then placed in the 50ml beaker using a volumetric pipette. The 50ml beaker with the 10ml of water was then weighed again and the initial mass of the beaker was subtracted from this mass to obtain the mass of the 10ml of water. With the volume and the mass of the water now known, density was calculated using d = m/V and recorded in g/ml. This process was then repeated to check for precision and compared to standard values to check for accuracy. Standard values were obtained from CRC Handbook, 88th Ed.

Calibration tells you if the instrument is accurate or not. Based on that knowledge, you can adjust it to get a more accurate reading.

Before beginning an experiment, it is good to calibrate any equipment that needs calibration. This ensures that results obtain will be as accurate as possible or as near to the true value. All equipment should be inspected to ensure that there are no chips, cracks or general damage to the equipment as these could cause problems during the experiment which could affect the overall results gained. Equipment such as burettes, pipettes, flasks and beakers must be rinsed with distilled water to get rid of any impurities in the equipment. If solutions are to be poured in any piece of equipment then the equipment should also be rinsed out with the solution being used, this will maintain the pH level in the instrument. Once a solution is transferred from the pipette to the flask, touching the tip of the pipette on the side of the flask will drain any extra drops that may still remain on the tip of the pipette.

The volume of a small test tube and a thin-stemmed pipet were determined in this section of the lab. Water was poured into a small test tube until the water reached the very top edge of the test tube. The test tube was then emptied into a plastic 25 mL graduated cylinder and volume was measured and recorded into data table 3. A think-stemmed pipet was completely filled with water. Drops were carefully counted and emptied into the empty plastic 25 mL graduated cylinder until the water level reached 1 mL. The number of drops in 1 mL was recorded into data table 3. The thin-stemmed pipet had a total volume of 4 mL and that was also recorded into data table 3.

A spectrophotometer is an instrument which measures the amount of light of a specified wavelength which passes through a medium. This instrument is usually used for the measurement of reflectance of solutions. Light is separate into different wavelengths and is being passed through the sample solution. The sample solution will have its own wavelength and will absorb a certain amount of light. The higher the molecular concentration, the higher the absorbance value.

At first I was unsure on how these were different but after using the lab program and following the instructions I can now see that different balances are needed for difference situations. Some that may require a more precise measurement where as others may not need such accurate measurements.

     Conventional Liquid Chromatography is most commonly used in preparative scale work to purify and isolate some components of a mixture. It’s also used in ultra trace separations where small disposable columns are used once and then discarded. Analytical separations of solutions for detection or quantification typically use more sophisticated high-pressure liquid chromatography instruments.

A volumetric pipette & measuring cylinder can be calibrated by just weighing the water they deliver. As for volumetric flask, the weight of an empty flask is recorded. Next, weigh the flask after filling it with water to the mark.

concentration, record the absorbance readings at a fixed wavelength, and plot the absorbance vs. concentration data. The wavelength of 520 nm was selected for experiment Part