Chemistry Lab Studyguide

Experiment 1: Method 1 (balance, volume by ruler)

• Mass of acrylic = 6.153g

• Diameter of acrylic = 1.90cm

• Radius of acrylic = .95cm

• Height of acrylic = 1.90cm

• Volume of acrylic = 5.40cm³

  • (pi x r² x h)

• Density of acrylic in g/cm³ = 1.14 g/cm³

  • (d = m/v)

Experiment 1: Volume by water displacement

• Initial volume of water in 100.0mL graduated cylinder = 50.0mL

• Final volume of water with acrylic submerged = 55.0mL

• Volume of acrylic = 5.0cm³

• Density of acrylic in g/cm³ = 1.23g/cm³

Experiment 1: Density by Neutral Buoyancy

• Syringe calibration trials

  • .9983 g

  • 1.0185 g

  • 1.0157 g

Experiment 1: Density of neutrally buoyant solution

• Initial volume of thiosulfate solution = 50.00 cm³

• Approximate volume added to attain neutral buoyancy = 2.0 mL

Experiment 1: Neutrally buoyant solution measurements

• trial 1 = 1.3476 g

• trial 2 = 1.3468 g

• trial 3 = 1.4091 g

• Average mass of solution = 1.3678 g

• Standard deviation

• Density of acrylic

Experiment 1: Accuracy and Precision

• Density by caliper (% diff.) = -0.03%

• Density by water displacement (% diff) = 4.34%

• Density by neutral buoyancy (% diff) = 15.92%

• Accepted = 1.18 g/cm³

• Equation = calculated-actual/actual x 100

Quiz 1

• Who should wear goggles

  • Everyone in the lab

• If you notice a classmate not following safety protocol you should

  • Say something to them/ your instructor

• When is it ok to sit on the bench/floor

  • You are about to pass out

• When should you remove your safety goggles

  • Everyone finished the experiment

• If your clothes catches fire you should

  • Stop, drop, roll or use safety shower

Experiment 2: Determination of mass percent of ammonium chloride

• Mass of evaporating dish and original sample = 42.2037g

• Mass of evaporating dish = 39.4652g

• Mass of original sample = 2.7385

• Mass of evaporating dish after subliming NH4Cl = 42.0562g

• Mass of NH4Cl = 0.1475

• Percent of NH4Cl = 5.386%

  • mass of NaCl/mass of original sample

Experiment 2: Determination of mass percent of sodium chloride

• Mass of erlenmeyer flask and NaCl = 125.1824g

• Mass of erlenmeyer flask = 92.0076

• Mass of NaCl = 1.5412g

• Flask + NaCl dry = 93.5488

• Percent of NaCl = 56.278%

  • mass of NaCl/mass of original sample

Experiment 2: Determination of mass percent of silicon dioxide

• Mass of evaporating dish and SiO2 and watchglass = 81.7474g

• Mass of evaporating dish and watchglass = 78.6524g

• Mass of SiO2 = 0.9188g

• Watchglass = 39.1872g

• Percent of SiO2 = 33.55%

  • mass of SiO2/mass of original sample

Experiment 2: Determination of percent recovery

• Mass of original sample = 2.7385g

• Mass of determined = 2.6075

  • NH4CL+NaCl+SiO2

• Differences in these weights = 0.1310g

  • Original - recovered

• Percent of recovery of matter = 95%

  • g matter recovered/g original sample x 100

Quiz 2

• Fatima adds 49.33mL water to a cylinder then submerges the slug m=8126.7mg. The water rises to 55.8mL. What is the density of the slug to the correct sig figs?

  • 1.3g/mL

• An acrylic slug with density of 1.18g/mL is dropped into a graduated cylinder containing glycerin solution with density of 1.18 g/cm³? What will happen?

  • It will remain suspended in the middle

• In the neutral buoyancy method, when it isn’t sinking or floating, this means

  • Same density

• Water level in a 100mL cylinder increased by 6.4mL after a slug is dropped. The slug weighs 7.68g, what is the density?

  • 1.20 g/mL

• Main advantage of water displacement

  • Works regardless of shape or size

Experiment 3: Household Ammonia

• Effect of household ammonia on dry litmus = no change

• Effect of household ammonia on moist litmus = red litmus turned blue

• Effect of NH4Cl on litmus = no change

• Effect of NH4Cl + NaOH on litmus = red litmus turned blue

• Fertilizer has ammonium salt

  • Add NaOH and test using red moist litmus paper

• Smelling salts = turned red moist litmus blue

Experiment 3: Baking Soda + NaHCO3

• Baking soda + H2SO4 = H2SO4 caused it to fizz up

• Baking soda + vinegar = Vinegar caused it to fizz up

• Chalk has carbonate ions

  • Add HCl test for escaping gas by suspending drop of Ba(OH)2

Experiment 3: Table Salt, NaCl

• Effect of H2SO4 on table salt = fizzing, strong odor

• H2SO4 (l) + 2NaCl (s) → 2HCl (l) +NaSO4 (aq)