SCC lab 1-4

how do you dilute acids?

add acids to water never add water to acids. can cause splash-safety hazard

how do you heat flammable organic solvents

never use naked flame, use steam bath or heating mantle

how do you identify odours of gases

avoid inhaling. gently waft the gas

what is the procedure after getting chemicals in your eyes

go to the eyewash station and wash eyes for 15 minutes

name of the utensil used to transfer small amounts

metal spatula

if you poured too much, what is the process to discarding the excess product

discard excess in rubbish bin, may cause contamination

4 types of glassware used to measure volume

1. measuring cylinders

2. pipettes

3. burettes

4. volumetric flask

what is a measuring cylinder

used to deliver variable approx volumes of liquid with limited accuracy

what is a pipette

used to deliver a definite volume of liquid with a high degree of accuracy

what is a burette

variable volumes with fairly high accuracy. majorly used in titrations in volumetric analysis

what is a volumetric flask

preparing definite volumes of solution with a high level of accuracy in preparation of standard solution

differentiate between accuracy and precision

accuracy: measures how close a result is to the true value

precision: measures how close a series of measurements are to each other, consistency

why is exponential notation important in chemistry

convenient to write numbers in abbreviated forms

define sig fig

digits known with certainty plus the first digit that is uncertain. e.g 5.25 g, 3rd number (5) is uncertain.

what was the purpose of experiment 2

to introduce various chemical techniques and to prepare copper sulfate from copper nitrate

what was the first step of exp 2

1. production of copper hydroxide by precipitation

2. dissolve copper nitrate and dissolve with distilled water

3. add sodium hydroxide

2nd step of exp 2

conversion of copper hydroxide to copper oxide by heating copper hydroxide solution on hot plate

decant liquid to keep only black solid of CuO

3rd step of exp 2

neutralisation of copper oxide by adding sulphuric acid (H2SO4), forming a blue solution copper sulphate

4th step of exp 2

evaporation of water to form crystals hydrated copper sulphate.

add boiling chips and heat solution on hot plate. pour in plastic tray and allow crystals to form

explain a neutralisation reaction

reaction between an acid and a base

explain a metal displacement reaction

a more reactive metal pushes out a less reactive metal out of its compound

explain decomposition of a carbonate by heating

placed copper carbonate in test tube and heat it, allowing gas to pass through to another test tube

explain a reaction between carbonate with an acid

calcium carbonate + HCl in one test tube, let gas pass through another test tube

explain a reaction between reactive metal with a dilute acid

Mg ribbon + HCl in one test tube, collecting gas through inverted test tube, use flame for the pop test

3 commonly used techniques to collect gases

• downward displacement of air

• upward displacement of air

• displacement of water

explain the production of hydrogen gas:

• downward displacement of air because H2 is less dense than air

• Mg + HCl → H2 + MgCl2

• pop test

explain the production of O2:

• downward displacement of water due to similar density as air

• 2H2O2 → 2H2O + O2

• manganese oxide mixed with hydrogen peroxide

what is the purpose of manganese oxide?

serves as a catalyst, lowers activation energy required for the decomposition of hydrogen peroxide

describe the production of carbon dioxide

• upward displacement of air because CO2 denser than air

• CaCO3 + 2HCl → H2O + CaCl2 + CO2

describe pH of CO2

acidic, pH went from green neutral to red (acidic)

describe ignition of hydrogen, oxygen and CO2:

hydrogen: flammable

oxygen: flammable

CO2: non flammable

identification test for H2, O2, CO2

H2: pop test

O2: glowing stick will ignite in presence of O2

CO2: universal indicator went green neutral to red

describe solubility of CO2

CO2 is soluble, forming carbonic acid

explain the limewater test for CO2:

CO2 gas is bubbled through limewater, if CO2 is present, limewater turns a milky colour bc insoluble calcium carbonate is formed:

CO2 + Ca(OH)2 → CaCO3 + H2O