Solution: Grams Essay

Submitted By aisha271005
Words: 721
Pages: 3
Open Document
Examples: Making Solutions

Two simple examples are presented here. A third example is of a complex solution for which the description lists the concentrations of components using different expressions.

Weight in volume: Prepare 2 liters 0.85% sodium chloride
With 1% defined as 1 gram per 100 ml, 0.85% is 0.85 grams per 100 ml. Since two liters is 20x the volume of 100 ml, we need 20 x 0.85 grams which is 17 grams NaCl. For this quantity we can use a top loading balance or even a trip balance.
A typical electronic balance is accurate to one hundredth of a gram, which is sufficiently accurate for weighing out 17 grams. First we "tare" the instrument by placing a weigh boat onto the pan and setting it to “zero.” We don't want to contaminate our chemical stocks, so we either clean the spatula or spoon before dipping it into the container or we simply shake the chemical out onto the boat.

Suppose that we tap out 16.97 grams of NaCl. Should we go to the trouble to get that last 0.03 gram? Nope! Consider that if it was necessary to be more accurate, we would describe the formula as something like 0.846% NaCl, or maybe 0.8495%. If there is some advantage to being precise then we should exercise precision, otherwise trying to be too precise just wastes time.

Remember how to use significant digits? Seventeen grams means greater than 16.5 grams and less than 17.5 grams. If we wanted to be more accurate we would write “17.0” grams, meaning greater than or equal to 16.95 grams and less than or equal to 17.05 grams.

Molarity: Prepare 200 ml of 70 mM sucrose
Suppose that you need 200 milliters of a 70 mM solution of sucrose. Two hundred milliliters is 0.2L and 70 mM is 0.07M. The molecular weight of sucrose can be determined from its chemical formula, namely C12H22O11 and the atomic weights of carbon, hydrogen, and oxygen. The formula weight for sucrose is identical to its molecular weight, namely 342.3 grams per mole. A 1M solution would consist of 342.3 grams sucrose in one liter final volume.

A concentration of 70 mM is the same as 0.07 moles per liter. Take 0.07 moles/liter times 342.3 grams per mole and you have 23.96 grams needed per liter. To make 200 milliliters of your solution multiply grams/liter by liters needed. Since 200 milliliters is 0.2L, multiply 23.96 grams by 0.2L to get 4.792 grams needed. Since a typical top loading electronic balance displays mass to the nearest 0.01 gram, the amount to be weighed should be rounded to 4.79 grams, although it is perfectly acceptable and perhaps even preferable to round to 4.8 grams.

Complex solution: Prepare a sample buffer for SDS-PAGE

The following formula describes the composition of the 2x concentrated buffer that we use to denature proteins for electrophoresis. The formula descriptions v/v or w/w would not be listed in a methods section since it is obvious which
Show More

Related Documents: Solution: Grams Essay

Essay about biology lab

Mass of a Solution Due to how hypertonic it is Problem: Which solution is more hypertonic? Hypothesis: If the solution in the bag is more hypertonic the mass change should be greater. Intro: The movement of molecules from an area of greater concentration to an area of less concentration is called Diffusion. Osmosis is the diffusion of water through a selectively permeable membrane from an area with greater concentration of water to an area with less concentration. A Hypertonic Solution is a solution…

Words 366 - Pages 2

Nardostachys Jatamansi Lab Report

ml of extract solution contain = X gram extract 100 ml of extract solution contain = X 100/10 =10X gram extract 2 gram powdered drug contain = 10X gram extract 100 gram powdered drug contain = 10X × 100/2 gram extract = 500X % X = difference in pre weight and final weigh Ethyl acetate…

Words 1091 - Pages 5

Iron And Copper Reaction Lab Report

reaction between copper(II) solution and iron by combining 2 bright box #6 nails with a CuSO4 solution. According to the ion chart, iron can only form the ions of +2 and +3, so that means the iron and copper solution reaction can be expressed in the formula CuSO4+Fe→FeSO4+Cu or 3CuSO4+2Fe→Fe2(SO4)3+3Cu for irons +2 ion or +3 ion, respectively. Next, the mass of the sample changed as it dried because it was left out by the window, meaning that some of the copper solution evaporated into gas, meaning…

Words 864 - Pages 4

Synthesis of Aspirin Essay

|Trial 2 | |Initial observations of acetic anhydride |Transparent, aqueous solution. |Transparent, aqueous solution. | In trial 1, the appearance and state of acetic anhydride was noted at the beginning of the experiment; acetic anhydride is a transparent aqueous solution. The same observation was made in trial 2. Observations of sulfuric acid – Table 3 | |Trial…

Words 5248 - Pages 21

6.03 Calorimetry Lab

For the first reaction, which is NaOH(s) → NaOH(aq), I would first need to measure out the required .041 moles of NaOH, which would weigh 1.65 grams. I would then measure out 41 milliliters, so that when I mixed the two, my concentration of NaOH in my aqueous solution will be 1M. In all, this should weigh about 41.8 grams when mixed together; however, prior to pouring the NaOH, I will first need to measure the temperature of the water itself with the calorimeter; I will do this at least five times…

Words 469 - Pages 2

Chem 1212k Lab Report Essay example

compound. Added 5 grams of cobalt carbonate to 20 mL of hrdrobromic acid in a beaker. Noticied a slight color change to dark purple. Solution frothed after it settled I mixed in 15mL water and…

Words 1342 - Pages 6

Oxygen and Manganese Sulfate Monohydrate Essay

taught students more understanding on dimensional analysis and correct units. Another purpose was the use of balancing and understanding equations. The ability to recognize a chemical equation as having a reaction and what the reaction produces. The solution in an oscillation reaction changes colors from white - amber - blue and back to white. In the reaction, gas is released and a solid should form. The experiment had a lot of success and changed colors for approximately 10-20 minutes. Introduction:…

Words 900 - Pages 4

Nanalytical Chemistry Essay examples

analytical methods iv. Uncertainty/error 6. Interpretation and reporting 7. Drawing conclusios * Types of Analysis * Gravimetric = measure mass of analyte or related compound * Volumetric = measure volume of solution containing sufficient reagent to react completely with the analyte * Electroanalytical = measure electrical properties such as potential, current, resistance and quantity of electricity * Spectroscopic = measurement based on interaction…

Words 635 - Pages 3

Coral Mass Lab

Forthcoming, the pH of different combinations of solutions were tested by submerging pH papers into the varying solutions, and matching the color to the color guide that depicted different pH levels to find the best concentration ratio that would result in the most array of changes. One of the original concentrations included a 25% vinegar solution, but it provided a very similar pH to the 50%. After multiple trials of different concentrations, it…

Words 1545 - Pages 7

Essay On Exponential Notation

perform a lot of conversions involving moles (mol). Whether you're converting from moles to grams, moles to volume, or moles to particles (atoms or molecules), use this quick guide to remind you of how to do each type of mole conversion: • Converting from mass (grams) to moles: Divide your initial mass by the molar mass of the compound as determined by the periodic table. • Converting from moles to mass (grams): Multiply your initial mole value by the molar mass of the compound as determined by the…

Words 3249 - Pages 13