Report 1

Chem134L 2023 Report 1 Report 1 Aims of the experiment and brief overview of the experimental method Aims: In experiment 1, “The Density of Solids,” the purpose was to find the density of the given cubes using a digital balance to find their individual mass and a ruler to measure their side lengths. Calculating the density of the cubes allowed us to explore each cube’s distinct properties and gave us the opportunity to develop lab skills. In experiment 2, “The Density of Water,” the purpose was to determine the density of water using two different measuring methods: the pipette and burette method. Both methods allowed us to measure different volumes of water and mass to determine the density. In the second part of experiment 2, “Using Reactions to Identify Ions in Solutions,” the purpose was to determine the identity of ions in the given “unknown” solutions (A-D). Four “unknown” solutions were run through several tests with five “known” solutions to test for ammonia. Methodology: Since density is a derived unit from mass and volume, various values were measured and recorded. In experiment 1, a ruler was used to measure the length, width, and height of each cube in centimeters to two decimal places. These measurements were then multiplied together to get the volume of each cube. Then, each cube was placed individually on a digital scale, which was used to measure its mass in grams. Density was calculated by dividing the mass (g) of the cube by the volume (cm^3) of the cube. In experiment 2, the density of water was found using two methods: the pipette and burette method. In the pipette method, deionized water was added to a plastic bottle in increments of 10 mL (from 0 mL to 50 mL*) from a graduated pipette, then was placed on an analytical balance after every increment to measure the mass of the bottle plus the added water. In the burette method, the same method was carried out using a burette to measure the volume of deionized water added. The mass and volume of the water were recorded to later calculate the density of water. In the second part of experiment 2, four “unknown” aqueous ionic solutions were reacted with the five “known” aqueous solutions, 0.1M AgNO3, 0.1M BaCl2, 0.1M CuSO4, 3.0M NaOH, and 3.0 HCl. Observations from the reactions, such as formation of a precipitate, change in color of aqueous solutions, flame color in flame tests, and bubbling in the ammonia test were recorded in the lab notebook to later identify which ions were involved in each reaction. Results and calculations Pay close attention to the precision for all the measured and calculated values throughout and be careful to include units with any values 1

Chem134L 2023 Report 1 Experiment 1: The Density of Solids Table 1. Complete this table with the data you collected on the solid samples. Sample Length/cm Width/cm Height/cm Volume/cm 3 Mass/g Density/gcm -3 Tungsten (W) 1.00 1.00 1.00 1.00 19.33 19.3 Silicon (Si) 1.00 1.00 1.00 1.00 2.32 2.32 Dark Grey (Unnamed ) 2.45 2.45 2.50 15.0 174.62 11.6 The Gold One 2.50 2.50 2.45 15.3 130.94 8.56 Titanium (Ti) 1.00 1.00 1.00 1.00 4.91 4.91 Silver- colored One 2.50 2.50 2.50 15.6 40.55 2.60 White-ish Gray One 2.50 2.50 2.50 15.6 101.09 6.48 Nickel (Ni) 1.00 1.00 1.00 1.00 9.09 9.09 Sample calculation One sample calculation is sufficient. Please show how you set up your calculation. Volume of Tungsten cube = 1.00 cm^3 Set-up: V = s^3 or V= (length) (width) (height) V = (1.00 cm) (1.00 cm) (1.00 cm) = 1.00 cm^3 Density of Tungsten = 19.33 g/cm^3 Set-up: D = m / V D = (19.33 g) / (1.00 cm^3) = 19.33 g/cm^3 Experiment 2: The Density of Water The buret method Complete this table with the data you collected.Table 2. Buret readings, mass, and density Trial Vol intital /mL Vol final /mL Vol transferred /mL Mass of Mass of water Density/g/mL 2

Chem134L 2023 Report 1 Trial Volume transferred /mL Mass of bottle+cap+water/g Mass of water transferred/g Density/g/mL 1 10.00 41.9460 9.709 0.9709 2 10.00 51.5766 9.631 0.9631 3 10.00 61.2228 9.646 0.9646 4 10.00 70.9371 9.714 0.9714 5 10.00 80.7135 9.776 0.9776 Mass of empty bottle + cap: 32.2361 g Sample calculations One sample calculation is sufficient. Please indicate which trial you use and show how you set up your calculation. For trial 2: Mass of water = Mass of (bottle + cap + water) final – (mass of bottle + cap + water) intial = Mass of water = 51.5766 g - 41.9460 g = 9.6306 g  9.631 g Density of deionized water = D = m / V D = 9.6306 g / 10.00 mL = 0.96306 g/mL  0.9631 g/mL Calculate the mean density of deionized water by the pipette method. Please show how you set up your calculation. Mean density = ( Σ of densities from each trial ) / ( # of trials) Mean density = (0.97099 g/mL + 0.96306 g/mL + 0.96462 g/mL + 0.97143 g/mL + 0.97764 g/mL) / (5 trials) = 0.970088 g/mL  0.9701 g/mL Experiment 2: The Density of Water The graphical method Table 4. Cumulative volume - mass data by the buret method Trial # Volume of water transferred / mL Mass of water transferred / g 1 10.00 9.997 4

Chem134L 2023 Report 1 2 20.00 20.03 3 30.00 30.05 4 40.00 39.97 5 50.00 49.94 Table 5. Cumulative volume - mass data by the pipet method Trial # Volume of water transferred / mL Mass of water transferred / g 1 10.00 9.709 2 20.00 19.34 3 30.00 28.60 4 40.00 38.70 5 50.00 48.47 Plot, using a graphing program, the mass of water on the vertical axis versus volume of water on the horizontal axis using the cumulative data from the buret additions and, on the same graph, the data from the pipet additions and include your graph in this report . Plotting the cumulative volume versus the cumulative mass allows us to determine the density as the slope of our line.  Use different labels for each set of data points.  Include the best fit line through each set of points and show the equations of both straight lines along with their R 2 value on the graph.  Include an appropriate caption for the graph.  Prepare your graph in the format discussed in the prelab lecture 5

Chem134L 2023 Report 1 Experiment 2: Using Reactions To Identify Ions In Solution For each of the four solutions A-D, indicate the identities of the ions present in the solution and give any relevant flame colors. For each positive chemical test, include a balanced net ionic equation including states describing the reaction. Solution A The ions present in solution A were found to be potassium and iodide. Net ionic equation(s) Ag ( aq ) + ¿¿ + I ( aq ) − ¿¿  AgI ( s ) ❑ 2Cu + (aq) + 5I - (aq)  CuI (s) + I - 3(aq) Flame color: orange/purple Solution B The ions present in solution B were found to be ammonium and sulfate. Net ionic equation(s) Ba 2+ (aq) + SO 4 2- (aq)  BaSO 4 (S) OH - (aq) + NH 4 + (aq)  NH 3 (aq) NH 3 (aq)  NH 3 (g) Flame color: blue (no apparent change) Additionally, in the ammonium test, the litmus strip changed color from red to blue, which indicated the presence of the conjugate base NH 4 + (ammonia). Solution C The ions present in solution C were found to be lithium and chloride. Net ionic equation(s) Ag + (aq) + Cl - (aq)  AgCl (s) Flame color: bright and deep purplish red Solution D The ions present in solution D were found to be sodium and carbonate. Net ionic equation(s) 2H + (aq) + CO 3 2- (aq)  H 2 CO 3 (aq)  CO 2 (g) + H 2 O (l) Cu 2+ (aq) + CO 3 2- (aq) → CuCO 3 (s) 2Ag + (aq) + CO 3 2-( aq) → Ag 2 CO 3 (s) Ba 2+ (aq) + CO 3 2-( aq) → BaCO 3 (s) Flame color: orange 7

Chem134L 2023 Report 1 Reflection Questions Be brief in your answers. If you wish, you may consult with your TF, the instructors, and your classmates when you are formulating answers to these questions but when giving your answers make sure that your answers are your own. 1. Of the two methods used for measuring the volume of water, the buret or the pipet, which is easier? Which is more reliable? If you prefer, you may answer this question in two separate paragraphs, one for each method, listing each of their advantages and disadvantages but be sure to say which is, in your opinion, better. Out of the two methods, the pipette method is easier, however I prefer the buret method. The graduated pipette has 10.00 mL clearly marked, so it’s easier to measure the meniscus of the water to deliver a volume accurately reflecting 10.00mL. Contrary to the buret, where the second decimal place is an estimate, the graduated pipette delivers also a more reliable estimate of 10.00mL due to it being clearly marked. Though the graduated pipette is better at releasing smaller volumes because we have more control over the pipette bulb, I find using the buret stopcock valve to be more fun. Nevertheless, it can still be challenging to release a specific volume if the pipette bulb is pressed too quickly or if there is air that was not removed from the start. A buret is great for delivering volumes of a larger range. Because of the nature of the stopcock valve, it’s easier to accidentally release too much liquid into the container and must restart. The buret method requires more attention from start to end volume since you have to close the valve at the right time. 2. Does the density of a gas, liquid, or solid depend on temperature? If so, is any such variation likely to be large or small? Illustrate your answer with any examples you choose. The density of a substance, whether it’s a gas, liquid, or solid, does depend on temperature. In most cases, changing the temperature of a substance will result in the change of its density. For gases, the density if directly proportional to its temperature and pressure. According to the gas law (PV = nRT), as temperature rises (pressure and moles are constant), the volume of the gas will increase, which will lead to a decrease in density. For liquids, the density decreases as the temperature increases. This behavior is more common in liquids, but the change in density with temperature usually relatively small compared to gases. For water, however, becomes less dense as it approaches its freezing point, which is why ice floats on water. For solids, the density of solids generally increases with a temperature decrease. When a solid cools down, the particles become closely packed, leading to an increase in density. At lower temperatures, most solids are dense, even if the changes aren’t too drastic. 8