C7 - Further Chemistry

Question 1

Give two examples of when Gas Chromatography is used.

Answer 1

• When detecting banned substances in blood samples.
• When analysing oil spills to identify sources of pollution.

Question 2

When is chromatography used?

Answer 2

When you want to determine what unknown mixtures consist of.

Question 3

What is a standard solution?

Answer 3

A solution containing a precisely known concentration of an element or substance.

A known weight of solute is dissolved to make a specific volume.

Question 4

What is the formula for calculating percentage yield?

Answer 4

Percentage yield = (Actual yield / Theoretic yield) * 100.

Question 5

What are the 5 stages of chemical production?

Answer 5

1. Preparation of feedstocks (Starting materials).
2. Chemical synthesis.
3. Separation of products.
4. Handling of by-products and waste.
5. Monitoring purity.

Question 6

Why do we calculate R_f value?

Answer 6

Because it allows the identification of unknown substances, by comparing with R_f values of known substances under the same conditions.

Question 7

What is the formula for calculating percentage error of an experiment?

Answer 7

Range/Average * 100.

Question 8

What are the problems with The Haber Process?

Answer 8

High temperatures and pressures are expensive, dangerous and have a high carbon footprint.

Therefore, scientists are always looking to find new catalysts, particularly ones that would mimic natural enzymes.

Question 9

In Paper Chromatography, what is the stationary phase?

Answer 9

The medium that the solvent moves through (e.g: Paper).

Question 10

During chromatography, some substances may be colourless - how are these identified?

Answer 10

By using locating agents. These are chemicals sprayed on the chromatogram, that reacts with the spots to cause coloration, or allow the viewing of spots under UV.

Question 11

Give an example of a reversible reaction.

Answer 11

Ammonium chloride <–> Ammonia + Hydrogen Chloride.

NH₄Cl(s) <–> NH₃(g) + HCl(g).

Question 12

What are the 5 stages of Paper Chromatography?

Answer 12

1. If the substance you want to analyse is a solid, dissolve it in a suitable solvent.
2. Place a spot of the resulting solution onto a sheet of chromatography paper on the pencil line and allow it to dry.
3. Place the bottom edge of the paper into a suitable solvent.
4. The solvent will rise up the paper, and dissolve the ‘spot’, carrying it up the paper.
5. The different chemicals in the mixture separate based on their properties and molecule sizes.

Question 13

State the names of the two simplest alcohols and their molecular formula?

Answer 13

• Methanol - CH₃OH.
• Ethanol - C₂H₅OH.

Question 14

What are the two types of error - and how can you come about them?

Answer 14

• Systematic error - Repeat measurements are consistently too high or too low.
• Could be caused by having an incorrectly zeroed balance on the scales. All results would be incorrect by the same amount.
• Random errors - Repeat measurements give different values.
• Could be caused by one-off errors or when the meniscus isn’t on the calibration line.

Question 15

State 3 ways ethanol is used on an industrial scale.

Answer 15

• Feedstock.
• Solvent.
• Fuel.

Question 16

Explain how ethanol can be produced using biotechnology.

Answer 16

1. Create genetically modified E. coli bacteria.
2. Feed the bacteria sugars within waste biomass (e.g: Wood waste, corn stalks and rice hulls), which they will convert to ethanol.

Question 17

What is the standard reaction for:

Acid + Base –> ____________?

Answer 17

Acid + Base –> Salt + H₂O.

Additional details taken from C6 flashcards:

• When an acid reacts with an alkali, a salt and water are always made.
• The Hydrogen ions (H+) and Hydroxide ions (OH-) join up to form Water (H+ + OH- –> H₂O).
• The negative ion from the acid and the positive ion from the alkali are left in solution to form the salt (e.g: Na+ acid, Cl- alkali).

Question 18

What is the end point on a pH graph?

Answer 18

The point where a rapid change in pH occurs.

Question 19

What does standard procedures cover?

Answer 19

• Collecting samples.
• Storing samples.
• Preparing samples for analysis.

Question 20

In Paper Chromatography, what is the mobile phase?

Answer 20

The solvent.

Question 21

What is the standard reaction for:

Acid + Metal Carbonate –> ________?

Answer 21

Acid + Metal Carbonate –> Salt + H₂O + CO₂.

Question 22

What is the standard reaction for:

Acid + Metal –> _____________?

Answer 22

Acid + Metal –> Metal Salt + H₂.

Question 23

How do companies improve the yield during The Haber Process?

Answer 23

Unreacted nitrogen and hydrogen is recycled, which is much more cost effective than leaving the reaction long enough to reach a dynamic equilibrium.

Question 24

What is another method of finding out the volume of an acid required to neutralise an alkali?

Answer 24

Use a pH probe.

Question 25

In **Gas Chromatography**, what is the **stationary phase**?

Answer 25

A **microscopic layer of liquid** on an **unreactive solid support**.

Question 26

**State** some **uses of ammonia**.

Answer 26

Any of the following: * **Fertilisers**. * **Explosives**. * **Dyes**. * **Medicines**. * A variety of other essential chemicals.

Question 27

**Carboxylic acids** get their **properties** from the **functional group \_\_\_\_\_\_\_\_\_\_\_**.

Answer 27

**Carboxylic acids** get their **properties** from the **functional group** **-COOH**.

Question 28

What are the **6 main stages of a quantitative analysis**?

Answer 28

1. Choose an **analytical method** and take a **sample** that **represents the bulk material**. 2. Accurately **measure out the sample**. 3. **Dissolve** the sample if it's a **solid**. 4. Measure a **property** of a solution that's **proportional** to the amount of chemical in the sample. 5. **Calculate** a value from the measurements. 6. **Estimate** the **uncertainty** of your results.

Question 29

**State** examples of **bulk chemicals** *(Chemicals produced on a large scale)*.

Answer 29

* **Ammonia** *(NH₃)*. * **Sulfuric acid** *(H₂SO₄)*. * **Sodium Hydroxide** *(NaOH)*. * **Phosphoric acid** *(H₃PO₄)*.

Question 30

Using a lower temperature and higher pressure enables a higher yield - why don't we use lower temperatures and higher pressures?

Answer 30

It is a compromise between **safety**, **cost**, **rate** and **yield**. **450^oC** is a compromise between **rate of reaction and yield**.

Question 31

What is the **formula for calculating concentration and mass**?

Answer 31

**Concentration (g/dm³) = Mass (g) / Volume (dm³)**. *(Rearrangable)*

Question 32

How do **plants get their nitrates**, and what is the **problem with this**?

Answer 32

Plants get nitrates when **nitrogen-fixing bacteria convert N₂ in the air to nitrates using enzymes as catalysts**. However, this process is not sufficient enough to feed the world's population, so we use **synthetic fertilisers**.

Question 33

**State** the **names** of the **two simplest carboxylic acids**, and their **molecular formulas**.

Answer 33

* **Methanoic acid** - **HCOOH**. * **Ethanoic acid** - **CH3COOH**.

Question 34

**Carboxylic acids** are **_strong/weak_** acids.

Answer 34

**Carboxylic acids** are **_weak_** acids.

Question 35

**Alkanes** do **_not_** **react with aqueous reagents**. **Why** is this?

Answer 35

Because the **C-C** and **C-H** bonds are **strong** and **unreactive**.

Question 36

What are the **3 methods of estimating uncertainty in results**?

Answer 36

* Compare values from **repeat samples** to find the **range**. * Work out the **average value**. * State how **confident** you are about the results.

Question 37

Governments have a duty to protect **\_\_\_\_\_\_\_\_\_\_** and the **\_\_\_\_\_\_\_\_\_\_**.

Answer 37

Governments have a duty to protect **people** and the **environment**.

Question 38

What type of reaction is **more common**? **_Exothermic_** or **_Endothermic_**?

Answer 38

**_Exothermic reactions_** are **more common**.

Question 39

What is the **standard formula** for **alkenes**?

Answer 39

**C_nH_2n** ## Footnote where **n** is the number of carbon atoms.

Question 40

What is the **standard formula** for **alkane combustion**?

Answer 40

**Alkane + O₂ --\>** Combustion **--\> CO₂ + H₂O**. *N.B: The equation _must_ be balanced.*

Question 41

What are the **characteristics** and **uses** of **esters**?

Answer 41

* They have **distinctive smells**, responsible for the smells and flavours in fruits. * They are used in the **manufacture of perfumes and food products**. * They are also found in **solvents** and **plasticizers**.

Question 42

**State** two ways of **reducing environmental impacts** when using chemicals.

Answer 42

* Use chemicals that cause **minimal harm** to **people** and the **environment**. * Use chemicals that can be **broken down into non-toxic substances** that **aren't persistent** in the environment.

Question 43

**Titration** can be used to calculate the concentration of an acid by finding out how much alkali is needed to neutralise it. **Explain** how this method works.

Answer 43

# 1. **Fill a burette** with an **alkali of known concentration** and take an **initial reading**. 2. If you have been given a **solid acid**, accurately **weigh out a sample of it** and **dissolve it in an accurately measured volume of distilled water**. 3. Use a **_glass pipette_** to **measure the aqueous acid into a conical flask**. This allows you to know the precise amount of acid used. A **_white tile_** should be placed under this flask. 4. Add a few drops of the **indicator phenolphthalein** *(It should stay colourless)*. 5. Add **alkali from the burette** to the acid in the flash **drop by drop**. 6. **Swirl the flask to mix it well**. Near the end of the reaction, the indicator will **start to turn pink**. Only when it changes colour **permanently**, it means the acid has been **neutralised**. 7. Record the volume of alkali added by **subtracting the initial reading from the final reading**. 8. **_Repeat the experiment_** until you get **_concordant results_** *(+-0.1cm³)* to ensure accuracy. ## Footnote *N.B: This can be inversed to find the concentration of an alkali.*

Question 44

A **relationship** is set up between the **stationary** and **mobile** **phase** in chromatography - what is this called?

Answer 44

A **dynamic equilibrium**, set up for each component of the sample.

Question 45

What is meant by a **dynamic equilibrium**?

Answer 45

The point at which the **forward and backward reactions happen at the same rate**, therefore the **concentration of the products and reactants doesn't change**.

Question 46

What is the **standard procedure** of **storing samples**?

Answer 46

Containers should be: * **Clean and sterile**. * **Sealed**. * **Labelled**. * Stored in a **safe place**. This improves **reliability**, since there's less room for human error.

Question 47

What are the **uses of alcohols** *(Methanol and Ethanol)*.

Answer 47

**_Methanol_** * As a **chemical feedstock**. * In the **manufacture of cosmetics**. **_Ethanol_** * As a **solvent**. * As a **fuel**.

Question 48

**Explain** how **ethanol** can be produced through **fermentation**.

Answer 48

*N.B: This is how ethanol for use in alcoholic drinks is produced.* 1. **Water and yeast** are **mixed with natural sugars** at just above **room temperature**. 2. **Enzymes** found in the yeast **catalyse** the formation of **ethanol** and **carbon dioxide**. 3. The **carbon dioxide is allowed to escape** from the reaction vessel, but **air is prevented from entering it**. Note that the concentration of ethanol is limited by the **amount of sugar in the mixture** and the fact that **above a certain concentration, the ethanol kills the yeast**. The concentration can be increased by **distillation**, a process also used to produce **spirits** such as **whisky** and **brandy**.

Question 49

What is the **method** for **preparing esters**?

Answer 49

1. Add the correct **carboxylic acid** and **alcohol** to a **round-bottom flask**, along with a few drops of **concentrated sulfuric acid**. 2. Fit a **condenser vertically** to the flask and **heat** the mixture **strongly**. This is called **'heating under reflux'** because the vapours that evaporate are cooled and condense back into the flask. 3. The condenser is **rearranged** so that the mixture can be **heated gently** and the ester is then distilled off as a gas from the reacting mixture. 4. The **distillate** is transferred to a **separating funnel** where **aqueous sodium carbonate is added** in order to **neutralise any remaining acid**. The remaining acid is moved to the **aqueous layer** *(The lower, more dense layer of the two liquids)* and the **ester is left in the upper organic layer**. 5. The organic layer is then **transferred to a flask** and **solid anhydrous calcium chloride is added** to **remove any remaining water**. The **calcium chloride is removed by filtration** and a **final distillation** is then performed to obtain the **pure ester**.

Question 50

**\_\_\_\_\_\_\_\_\_\_** analysis is any method used to **measure** the amount of chemicals in a substance.

Answer 50

**_Quantitative_** analysis is any method used to **measure** the amount of chemicals in a substance.

Question 51

When **interpreting titration results**, you will need to **convert from cm³ to dm³** - how do you do this?

Answer 51

**Divide by 1000.** i.e: **1dm³ = 1000cm³**.

Question 52

**Vegetable oils** are usually **_saturated/unsaturated_** molecules. What are the **properties** of these molecules?

Answer 52

**Animal fats** are usually **_unsaturated_** molecules. **_Properties_** * **Double C=C bonds**. * **More reactive**.

Question 53

**Alcohols** get their characteristics due to the presence of the **functional group** **\_\_\_\_\_\_\_\_\_\_**.

Answer 53

**Alcohols** get their characteristics due to the presence of the **functional group** **_-OH_**

Question 54

What is the **formula** for **calculating atom economy**?

Answer 54

**Atom Economy = (Mass of atoms in useful products / Total mass of atoms in the reactants) \* 100**.

Question 55

**Carboxylic acids** generally have **_pleasant/unpleasant_ smells**.

Answer 55

**Carboxylic acids** generally have **_unpleasant_ smells**.

Question 56

**Compare** the **properties** of **alcohols** with **shorter chain lengths** to those with **longer chain lengths**.

Answer 56

**_Short chain length_** * *e.g: Methanol.* * **Low b.p** - **weak intermolecular forces**. * **Infinitely soluble** up to **propanol** *(After ethanol)*, then solubility decreases. **_Long chain length_** * *e.g: Octanol.* * **High b.p** - **strong intermolecular forces**. * **Less soluble in water** - behaves more like an alkane. * **Low density** - **floats on top of water** *(N.B: Shorter chain lengths have lower density, but the first 3 alcohols will dissolve in water - you don't need to know why because [it's complicated](http://chemistry.stackexchange.com/questions/10763/why-1-octanol-is-immiscible-with-water))*.

Question 57

Several companies now develop materials from **plants**, what are the **problems** with this?

Answer 57

* Lots of **land** is used. * **Fertilisers** use up a **lot of energy** during manufacture, and energy use should be minimised.

Question 58

What is the **standard reaction** for: **Acid + Metal oxide --\> \_\_\_\_\_\_\_\_\_\_\_\_?**

Answer 58

**Acid + Metal oxide --\> _Salt + H₂O_**.

Question 59

What is **retention time**?

Answer 59

Retention time is **used in Gas Chromatography** and is the **time taken** from when a substance is **injected** into the system to when it is **detected**.

Question 60

What is the **formula** for calculating **R_f value**?

Answer 60

**R_f value = Distance travelled by substance / Distance travelled by solvent**.

Question 61

What are the **advantages** of using **Gas Chromatography over Thin Layer Chromatography**?

Answer 61

* Greater **separating power**. * The ability to **separate complex mixtures**. * The ability to **produce quantitative data from very small samples** of liquids, gases and volatile solids.

Question 62

Describe the **reactions with sodium** for the following: * Alcohols. * Alkanes. * Water.

Answer 62

* Alcohols - Sodium **sinks**, **doesn't melt** and **steadily gives off Hydrogen**. * Alkanes - **No reaction**. * *Water - Sodium melts, rushes around on the surface and rapidly gives off Hydrogen (You should know this one).*

Question 63

What are the **social** and **economical benefits** of **Green Chemistry**?

Answer 63

**_Social_** * Cleaner **air quality**. * Cleaner **buildings**. * Improved **water quality** in rivers and lakes. **_Economic_** * Reduced **energy costs**.

Question 64

What is the **standard reaction** for **alcohols with sodium**?

Answer 64

**Alcohol + Sodium --\> Sodium (alcohol)oxide + Hydrogen** e.g: Ethanol + Sodium --\> Sodium ethanoxide + Hydrogen **2C₂H₅OH(l) + 2Na(s) --\> 2C₂H₅O^-Na⁺(s) + H₂(g)**.

Question 65

**Explain** how **ethene can be produced**, and how this can be **used to produce ethanol** through **chemical synthesis**.

Answer 65

1. **Crude oil** undergoes **fractional distillation**. 2. Long-chain **hydrocarbons** *(**alkanes**)* are **vaporised** and then **cracked** using a **catalyst** and **heat**. 3. The molecules are **purified** using **fractional distillation**. 4. The ethene that's produced can be used for a **feedstock** and the **remaining water is removed**. 5. Etene is then reacted with steam at a high temperature and pressure in the presence of a catalyst to produce ethanol: **C2H4(g) + H2O(g) --\> C2H5OH(g)**. Any unreacted products are **recycled** and used as the input.

Question 66

What are **3 methods for producing ethanol**?

Answer 66

* **Synthesis** *(Not sustainable - uses fossil fuels as raw material)*. * **Fermentation**. * **Biotechnology** *(Exploitation of biological process for industrial and other purposes, especially genetic modification)*.

Question 67

**The Haber Process** is used to produce **ammonia**. What is the **reaction** for this?

Answer 67

**N₂(g) + 3H₂(g) \<--\> 2NH₃(g)**.

Question 68

**The Haber Process** is a **reversible reaction** - how does this affect the **yield**?

Answer 68

The yield is only **15-30%**.

Question 69

**Animal fats** are usually **_saturated/unsaturated_** molecules. What are the **properties** of these molecules?

Answer 69

**Animal fats** are usually **_saturated_** molecules. **_Properties_** * **Single C-C bonds**. * **Unreactive**.

Question 70

**Describe activation energy** in terms of **breaking/making bonds** in **exo/endothermic reactions**.

Answer 70

In a chemical reaction, the **bonds in the reactants must be broken and new bonds made to form the products**. The **activation energy** is the **energy needed to break bonds to start a reaction**. * **Breaking** bonds is an **endothermic** process. * **Making** bonds is an **exothermic** process. In other words, chemical reactions that **absorb more energy to break the bonds in the reactants than is released when new bonds are made in the products**, are **endothermic**. On the other hand, chemical reactions in which **more energy is released when new bonds are made than was absorbed to break the old bonds**, are **exothermic**.

Question 71

What are the **optimum conditions** for **ethanol fermentation**?

Answer 71

* **Temperature**. * **pH**. * **No oxygen** *(Avoid producing ethanoic acid)*. *N.B: Optimum temperature and pH vary between enzymes.*

Question 72

What is **atom economy**?

Answer 72

A measure of the **amount of reactants that end up as useful products**.

Question 73

What is **precision**.

Answer 73

Precision is what we call **repeatability**. It's a measure of the **spread of the measured values**. A large spread leads to greater **uncertainty**.

Question 74

How are **chemical accidents prevented**?

Answer 74

By choosing substances that will **minimise the risk** of such accidents.

Question 75

What are **alkanes**?

Answer 75

A **group of hydrocarbons** where the carbon atoms are joined by **single carbon-carbon bonds**. They are **saturated** hydrocarbons for this reason.

Question 76

Chemists can also use **Thin Layer Chromatography** *(TLC)* - how is this **different** and what are the **advantages** of using it?

Answer 76

TLC uses a stationary phase of a **thin layer of absorbent material**, such as **silica gel**. This is supported on a **flat, unreactive surface**, such as a **glass plate**. **_Advantages_** * **Faster** runs. * More **even movement** of the **mobile phase through the stationary phase**. * A choice of **different absorbencies** for the **stationary phase**. This is why TLC usually produces **better separations** for a **wider range of substances**.

Question 77

What are the **optimum conditions** for **biotechnology**?

Answer 77

* Temperature between **25-37^oC**. * **Optimum pH level** should remain **constant**. This prevents the denaturing of enzymes.

Question 78

**State** examples of **fine chemicals** *(Chemicals produced on a small scale)*.

Answer 78

* Drugs. * Food additives. * Fragrances.

Question 79

Provide the **names** and **formulas** for the **first 4 alkanes**.

Answer 79

* **Methane** - **CH₄**. * **Ethane** - **C₂H₆**. * **Propane** - **C₃H₈**. * **Butane** - **C₄H₁₀**.

Question 80

What are the **4 stages** of **Gas Chromatography**?

Answer 80

1. **Dissolve** your sample into a **solvent**, which is injected into one end of the **glass column** *(The column is actually wound into a coil in most cases so that it fits into the **oven**)*. 2. An **unreactive gas** - usually **nitrogen** - carries the sample through the column. 3. Different substances in the sample travel through the column at **different speeds** due to their **different solubilities**, and so become **separated** from each other. 4. The separated substances leave the column one after the other. As they leave, they are detected by a **detector**.

Question 81

What is **accuracy**?

Answer 81

How close a result is to its **true value**.

Question 82

What are the **typical reactor conditions** in **The Haber Process**?

Answer 82

* **Iron** catalyst. * **200 atmospheres** pressure. * **450^oC** temperature.

Question 83

In **Gas Chromatography**, what is the **mobile phase**?

Answer 83

The **carrier gas** - usually nitrogen.

Question 84

When **interpreting titration results**, you may be asked to use **relative formula masses**. How would you do this? e.g: A titration is carried out and **35cm³ of sulfuric acid of concentration 60g/dm³ neutralises 25cm³ of sodium hydroxide**. Calculate the **concentration** of **sodium hydroxide**. To save you having to look it up, I will give the RFM's: * **H₂SO₄ - 98**. * **NaOH - 40**.

Answer 84

1) Work out the **RFM's of the acid and alkali**. 2) Write down the **equation**. This allows you to calculate the **mass of acid which reacts with the mass of alkali**. 3) Work out the **mass of the acid** *(Known concentration)* used in the titration using your rearranged equation **Mass = Concentration \* Volume**. 4) Work out the **mass of alkali** *(Unknown)* used in the reaction. 5) Work out the **concentration** using your equation for concentration - if you need a reminder, it's **Concentration = Mass/Volume**. **_Solution to example_** 1) **H₂SO₄** = 2+32+(4\*16) = **98**. **NaOH** = 23+16+1 = **40**. 2) H₂SO₄ + 2NaOH --\> Na₂SO₄ + 2H₂O. 3) Mass = Concentration \* Volume. 60g/dm³ \* (35cm³/1000) =**2.1g**. 4) If 98g of sulfuric acid reacts with 80g of sodium hydroxide, then **2.1g reacts with 2.1/98 \* 80g = 1.7g of sodium hydroxide**. 5) Concentration = Mass/Volume. 1. 7/(25cm³/1000) =**68g/dm³**.

Question 85

What is a **chromatogram**? How are they **used**?

Answer 85

A chromatogram is what's formed when the **chemicals come out of solution and bind to the stationary phase**. They are compared to **standard reference materials** *(Other chromatograms)* of known substances to **identify the different chemicals**.

Question 86

What are **alkenes**?

Answer 86

Another group of **hydrocarbons** that have **reactive C=C double bonds**. They're described as **unsaturated**.

Question 87

Name some **mistakes that could occur when gathering results** during an experiment.

Answer 87

Any of the following: * **Misreading a scale**. * **Forgetting to fill up a burette to the correct level**. * **Taking a thermometer out of the solution to read the scale**. * **Any other acceptable answer**.

Question 88

**Explain** the **method** to achieve a **standard solution**. Example to try: How would I make **250cm³ of standard solution with a concentration of 100g/dm³**?

Answer 88

*N.B: You are required to use the equation **Concentration (g/dm³) = Mass (g) / Volume (dm³)**.* 1. *Find out the mass you need to measure.* 2. **Measure out (the mass)** _25g_ **of the solid sample** in a **beaker**. 3. Fill the beaker with enough **distilled water** to **dissolve the solid** - but don't go over the volume you want yet. 4. Use a **short-stem funnel** and transfer the contents of the beaker into a **volumetric flask**. Wash the funnel and beaker with **distilled water**, and **pour the washings into the flask**. 5. Place the flask on a **level surface**, and **fill until the solution reaches (the volume)** _250cm³_. 6. Invert the flask to mix the contents and ensure an even concentration throughout. *You should be given the volume/mass, but if not default to 5g and 100cm³, as from the revision guide.*

Question 89

What is the **standard reaction** for **producing esters**.

Answer 89

**Carboxylic acid + Alcohol --\> Ester + Water.** This reaction is carried out in the presence of a **strong acid catalyst**.

Question 90

What does the **sustainability of a chemical process** depend on?

Answer 90

* The **_atom economy_**. * The use of **_renewable_** **feedstocks**. * Energy **inputs** and **outputs**. * **Health and safety** risks. * **Waste** prevention. * **Social**, **economic** and **environmental** effects/impacts.

Question 91

Give **two examples** of **naturally occuring esters**.

Answer 91

* **Fats** *(Esters of glycerol and fatty acids)*. * **Oils**.

Question 92

**\_\_\_\_\_\_\_\_\_\_** analysis is any method used to **identify** the chemicals in a substance.

Answer 92

**_Qualitative_** analysis is any method used to **identify** the chemicals in a substance.

Question 93

What are the **two types of solvent**?

Answer 93

* **Aqueous** - Water based. * **Non-aqueous** - Made from organic liquids such as **alkanes**.

Question 94

**State 3 regulations** the **government** controls.

Answer 94

* **Chemical processes**. * **Storage of chemicals**. * **Transporation of chemicals**. *Regulated by the Health and Safety Executive.*

Question 95

What is the **standard reaction** for **alcohols reacting with oxygen**?

Answer 95

*N.B: Alcohols **burn in air** because of the presence of a **hydrocarbon chain** (Combustion).* **Alcohol + Oxygen --\> Water + Carbon dioxide.** *N.B: You will be required to balance this.*