Laboratory Safety: Emergency Shower Procedure
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Questions and Answers

What is the main purpose of applying heat in organic chemical reactions?

To speed up the reactions

Why are organic compounds with low boiling points volatile?

Because they evaporate when heated

What should you do if you spill chemicals on your body?

Stand directly under the shower and pull the lever immediately to flush the affected area with plenty of water for 15 minutes.

What is the term used to describe the arrangement in which a reaction is carried out in a boiling solvent with the vapour being condensed and returned to the reaction vessel?

<p>Reflux</p> Signup and view all the answers

What is the purpose of the water sprayers in a chemistry lab?

<p>To flush away chemicals that are spilled on the body.</p> Signup and view all the answers

What is the purpose of the condenser in a reflux set-up?

<p>To cool and condense the vapours</p> Signup and view all the answers

What is the difference between reflux and distillation?

<p>Reflux completes a reaction, while distillation separates components of a mixture</p> Signup and view all the answers

What should you do if you get chemicals in your eyes?

<p>Place your eyes directly over the water sprayers and firmly push the lever. Continue this treatment for at least 15 minutes, even if you feel the irritation has subsided.</p> Signup and view all the answers

Why is it important to be familiar with chemical hazard symbols?

<p>It helps in having a better understanding of the safety aspects of any chemical being used.</p> Signup and view all the answers

Why is it essential to ensure the condenser is completely filled with water?

<p>To ensure efficient cooling</p> Signup and view all the answers

What happens to the vapours given off from the liquid reaction mixture in a reflux set-up?

<p>They change from gas phase back to liquid phase due to heat loss</p> Signup and view all the answers

What is a key safety precaution when working with flammable and combustible liquids?

<p>Eliminate ignition sources (sparks, smokes, flames, hot surfaces) when working with flammable and combustible liquids.</p> Signup and view all the answers

What should you do with contaminated clothing, jewellery, and shoes when treating a chemical spill?

<p>Remove all contaminated clothing, jewellery, and shoes.</p> Signup and view all the answers

What is the ultimate goal of using reflux in a chemical reaction?

<p>To give a higher yield of product</p> Signup and view all the answers

Why should you not place flammable and combustible liquids near open flames and spark-producing equipment?

<p>To prevent fires and explosions.</p> Signup and view all the answers

What should you do with storage areas for flammable and combustible liquids?

<p>Keep storage areas cool and dry.</p> Signup and view all the answers

What are the three main ways to make chemical processes 'greener'?

<p>Using different, less hazardous starting materials, using milder reaction conditions, better catalysts and less hazardous solvents, and using production methods with fewer steps and higher atom economy.</p> Signup and view all the answers

Why is it necessary to find an alternative to A or B in the reaction A + B → C + D if C is the only desired product?

<p>To avoid the production of D, which is an unwanted product.</p> Signup and view all the answers

What is the advantage of using alternative oxidising agents instead of chlorination for disinfecting water?

<p>They form less harmful products.</p> Signup and view all the answers

What does a high atom economy of a reaction indicate?

<p>That most of the reactants have been converted to the desired product.</p> Signup and view all the answers

What is the formula to calculate the atom economy of a reaction?

<p>Atom economy = (Molecular weight of the desired product / Sum of the molecular weight of all substances produced) x 100</p> Signup and view all the answers

Why do industrial processes aim to have high atom economy?

<p>Because it reduces the production of unwanted products and makes the process more sustainable.</p> Signup and view all the answers

What is the atom economy of the reaction Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)?

<p>1.45%</p> Signup and view all the answers

Why is it important to consider atom economy in chemical reactions?

<p>Because it helps to reduce waste, minimize environmental impact, and make the process more sustainable.</p> Signup and view all the answers

What percentage of an element is represented by its relative atomic mass?

<p>100%</p> Signup and view all the answers

In a mixture of two isotopes, how do you calculate the percentage abundance of one isotope if you know the relative atomic mass and the percentage abundance of the other isotope?

<p>You subtract the known percentage abundance from 100%</p> Signup and view all the answers

What is the formula used to calculate the relative atomic mass of an element?

<p><code>∑(Percentage Abundance × atomic mass)</code> / <code>100</code></p> Signup and view all the answers

If an element has two isotopes with masses 20 and 22, and the relative atomic mass is 20.18, how would you calculate the percentage abundance of each isotope?

<p>Set up an equation using the formula for relative atomic mass and solve for the percentage abundance of one isotope, then subtract from 100% to find the other</p> Signup and view all the answers

Why do the percentages of the isotopes in a mixture add up to 100%?

<p>Because they represent all the possible forms of the element</p> Signup and view all the answers

What information is needed to calculate the relative atomic mass of an element?

<p>The masses of the isotopes and their percentage abundances</p> Signup and view all the answers

What is the significance of the relative atomic mass of an element?

<p>It is a weighted average of the masses of the isotopes</p> Signup and view all the answers

How do you calculate the relative atomic mass of an element with multiple isotopes?

<p>Use the formula <code>∑(Percentage Abundance × atomic mass)</code> / <code>100</code></p> Signup and view all the answers

Why do anions have a larger radius than their respective atoms?

<p>When electrons are added to an atom, there is an increase in the electron-electron repulsion, causing the electrons to push apart and occupy a larger size. Additionally, adding electrons results in weaker nuclear pull as more electrons are now available with the same number of protons.</p> Signup and view all the answers

Why do cations have a smaller radius than their respective atoms?

<p>When electrons are removed from an atom, there is a decrease in electron-electron repulsion, resulting in stronger attraction between the nucleus and remaining electrons, which leads to a decrease in size.</p> Signup and view all the answers

Using the periodic table, arrange the elements from smallest to largest in the set: C, F, Br, Ga.

<p>F, C, Ga, Br ( smallest to largest )</p> Signup and view all the answers

Why does the Ca2+ ion have a smaller radius than the calcium atom?

<p>The removal of two electrons from the calcium atom results in a decrease in electron-electron repulsion, leading to stronger attraction between the nucleus and remaining electrons, causing a decrease in size.</p> Signup and view all the answers

Why does the O2- ion have a larger radius than the oxygen atom?

<p>The addition of two electrons to the oxygen atom results in an increase in electron-electron repulsion, causing the electrons to push apart and occupy a larger size.</p> Signup and view all the answers

Why is the chloride ion larger than the chlorine atom?

<p>The addition of one electron to the chlorine atom results in an increase in electron-electron repulsion, causing the electrons to push apart and occupy a larger size.</p> Signup and view all the answers

Why is the sodium atom larger than the chlorine atom?

<p>Sodium has a larger atomic radius than chlorine due to its position in the periodic table.</p> Signup and view all the answers

What is the trend of ionisation energy across a period?

<p>The ionisation energy increases across the period.</p> Signup and view all the answers

Study Notes

Laboratory Safety

  • In case of chemical spills, use safety showers to flush the affected area with plenty of water for 15 minutes to protect the eyes from further damage.
  • Remove all contaminated clothing, jewelry, and shoes.
  • Familiarize yourself with chemical hazard symbols to understand the safety aspects of any chemical being used.

Chemical Hazards and Safety Measures

  • Be aware of the safety measures for hazardous substances, such as:
    • Not placing flammable liquids near open flames and spark-producing equipment.
    • Eliminating ignition sources when working with flammable and combustible liquids.
    • Using the smallest amount of flammable liquid necessary in the work area.
    • Keeping storage areas cool and dry.
    • Storing flammable and combustible liquids away from incompatible materials.

Reflux

  • Reflux is a laboratory technique used to heat a reaction mixture while preventing the loss of volatile compounds.
  • The process involves boiling the reaction mixture, condensing the vapor, and returning it to the reaction vessel.
  • Reflux is used to speed up chemical reactions, especially in organic chemistry, and to increase the yield of products.

Difference between Distillation and Reflux

  • Reflux helps complete a reaction, while distillation separates components of a mixture.
  • Reflux is used to heat a reaction mixture, while distillation is used to separate and purify substances.

Green Chemistry

  • Green chemistry aims to make chemical processes more environmentally friendly.
  • Three ways to make chemical processes "greener" are:
    • Redesigning production methods to use different, less hazardous starting materials.
    • Using milder reaction conditions, better catalysts, and less hazardous solvents.
    • Using production methods with fewer steps and higher atom economy.
  • Atom economy measures the amount of reactants that become useful products, with higher atom economy indicating "greener" processes.

Calculating Atom Economy

  • Atom economy can be calculated using the formula: (Molecular weight of the desired product / Sum of the molecular weight of all substances produced) x 100.

Isotopes and Relative Atomic Mass

  • Isotopes are atoms of the same element with different numbers of neutrons.
  • Relative atomic mass is the weighted average of the atomic masses of the isotopes of an element.
  • The relative atomic mass of an element can be calculated using the percentage abundance of each isotope.

Cations and Anions

  • Cations are positively charged ions that are smaller than their respective atoms due to the stronger nuclear pull.
  • Anions are negatively charged ions that are larger than their respective atoms due to the weaker nuclear pull and increased electron-electron repulsion.

Ionic Radius

  • Ionic radius is the distance between the nucleus of an ion and its outermost electron.
  • Cations have a smaller radius than their respective atoms, while anions have a larger radius than their respective atoms.

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Year 13 Chemistry Textbook.pdf

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Learn how to properly use an emergency shower in a laboratory setting to flush away harmful chemicals and substances.

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