A REVIEW OF BASIC EXPERIMENT LABORATORY TECHNIQUES EQUIPMENT AND CHEMICALS: Equi

ID: 476224 • Letter: A

Question

A REVIEW OF BASIC EXPERIMENT LABORATORY TECHNIQUES EQUIPMENT AND CHEMICALS: Equipment 25 ml graduated cylinder 250 mL Erlenmeyer flask 13x100mm test tubes (5) 150 mL beaker 250 mL beaker 25 mL buret 10 mL volumetric pipet Evaporating dish Watch glass Crucible tongs. Glass stirring rod Test tube holder Wash bottle Rubber bulb Bunsen burner Iron ring. Striker uare mesh Buret clamp Stir plate Magnetic stir bar 100ml. graduated cylinder Chemicals Sodium chloride (NaC) solution solid magnesium (Mg) 0.1 M potassium chloride (KCI) 0.050 M hydrochloric acid (HCI) 0.1 M sodium nitrate (NaNO3) 1.0 M hydrochloric acid (HCI 0.1 M sodium carbonate (Na2CO's) 18 M sulfuric acid (H2soa) Phenolphthalein indicator solid ammonium chloride (NH4Cl) 0.1 M copper sulfate (CuSO4) 0.1 M barium chloride (BaCl2) INTRODUCTION: Experience shows that often students are lacking in the basic lab skills needed to be successful in a second semester laboratory. The reasons are varied, but may be as obvious as how long ago the student completed the first semester course. In other words, over time they have forgotten things and may just need a refresher. Regardless, in today's lab we will review numerous lab techniques. You will then demonstrate your ability to use those techniques to collect data and calculate the requested results. Equation writing is another area in which students often struggle. After reviewing the steps for writing a balanced chemical equation, you will perform several chemical reactions and write the resulting equations. DISCUSSION: A. USING A VOLUMETRIC PIPET: Typically, lab volumes are measured using either a beaker or graduated cylinder. However, sometimes a more precise measurement is required, in which case you might use a volumetric pipet. Volumetric pipets can be compared to a glass drinking straw, but with an expanded bubble in the middle to contain the volume.

Explanation / Answer

A) Analysis of sodium chloride solution

Part I – Determination of density

Data and results

Mass of evaporating dish plus watch glass 119.489 g

Mass of evaporating dish, watch glass and 130.078 g

sodium chloride solution

Mass of sodium chloride solution (130.078 – 119.489) g = 10.589 g

Volume of sodium chloride solution 10.00 mL

Density of sodium chloride solution mass/volume = (10.589 g)/10.00 mL

= 1.0589 g/mL (ans)

Part II – Determination of %NaCl

Data and results

Mass of evaporating dish plus watch glass 119.489 g

Mass of evaporating dish, watch glass and 121.356 g

sodium chloride solution

Mass of dry sodium chloride solids (121.356 – 119.489) g = 1.867 g

Volume of sodium chloride solution 10.00 mL

Concentration of sodium chloride solution (1.867 g)/(10.00 mL)*100

as per weight per volume = 18.67% wt/vol (ans).

B) Standardization of a calcium hydroxide solution

Equation:

2 HCl + Ca(OH)2 --------> 2 H2O + CaCl2

Data and results:

Trail 1

Trail 2

Molarity of hydrochloric acid (M)

0.050 (given in experimental section)

0.050

Volume of hydrochloric acid (mL)

10.0

Initial buret reading (mL)

0.0

Final buret reading (mL)

22.50

16.50

Volume of calcium hydroxide used (L)

(22.50 – 0.0) mL = (22.50 mL)*(1 L/1000 mL) = 0.0225 L

16.50 mL = 0.0165 L

Moles hydrochloric acid used

(10 mL)*(1 L/1000 mL)*(0.050 mol/L) = 0.0005

0.0005

Moles calcium hydroxide used

0.00025 (molar ratio of calcium hydroxide:HCl = 1:2)

0.00025

Concentration of calcium hydroxide (M)

(0.00025 mol)/(0.0225 L) = 0.0111

(0.00025 mol)/(0.0165 L) = 0.0151

Average concentration of calcium hydroxide (M)

0.0131