1 / 20

Limiting Reactants

Limiting Reactants. Today’s Lesson. Explain Concentration Complete Worksheet  Introduce Acids & Alkalis Textbook Questions – I bet you’ve missed those!!. Concentration. According to the dictionary (I know your all thinking kill me now!!), concentration is:

onslow
Download Presentation

Limiting Reactants

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Limiting Reactants

  2. Today’s Lesson • Explain Concentration • Complete Worksheet  • Introduce Acids & Alkalis • Textbook Questions – I bet you’ve missed those!!

  3. Concentration • According to the dictionary (I know your all thinking kill me now!!), concentration is: • thestrengthofasolution,espthe amount of dissolved substance in a given volume of solvent, usuallyexpressed in moles per cubic metre or cubicdecimetre(litre) • http://dictionary.reference.com/browse/concentration

  4. Normal English! • Concentration is how many particles are present in a given volume. • Chemists use a volume called the cubic decimeter – abbreviated as dm3. • The unit of concentration measurement is moles per decimeter cubed or mol.dm3 • Now we have the fun task of completing some example questions  (yay – now my life is complete!!)

  5. Example 1 • I have 2L of HCl at 1 mol.dm3 , what mass of HCl would I have • It’s easier than it looks. • First, find out the number of moles of HCl • Second, find out the Mr of HCl • Third, find out the mass by moles X Mr • Workings out on next slide:

  6. Example 1 Continued • I have 2L of HCl at 1 mol.dm3 , what mass of HCl would I have • 2L X 1 mol = 2 mol • Mr of HCl is 1 + 35.5 = 36.5 • Mass is 2 X 36.5 = 73g of HCl • It’s all done!

  7. Example 2 • What mass of KCl would I need to make a 0.2 mol/dm3 solution ? • So how do we work it out? • Work out the Mr of KCl • Work out the mol and volume (we already have this • To find out mass, mol X Mr

  8. Example 2 Continued • What mass of KCl would I need to make a 0.2 mol/dm3 solution ? • Mr of KCl is 39 + 35.5 = 74.5 g • Work out mol/dm3 ? It’s 0.2 mol/dm3 • Find mass. 0.2 X 74.5 = 14.9 g of KCl

  9. Calculating Unknown Concentrations! • Here is a new formula! We will be using it a big for acid/bases. • C1V1 = C2V2 • C1 = Concentration 1 • V1 = Volume 1 • C2 = Concentration 2 • V2 = Volume 2

  10. An Example • I have 25 cm3 of HF (an acid) at 0.8 mol / dm3. What mol / dm3 would I need for 50 mL of NaOH (a base)? • This is easier than it looks. Here is how we work it out! • Work out which is C1, C2, V1, and V2. • Manipulate the C1V1 = C2V2 equation.

  11. Explanation • I have 25 cm3 of HF (an acid) at 0.8 mol / dm3 . What mol / dm3 would I need for 50 cm3 of NaOH (a base)? • C1 = 0.8 mol / dm3 , C2 = ???, V1 = 25 cm3 , V2 = 50 cm3 • Equation C2 = C1V1 / V2 • C2 = 0.8 X 0.025 dm3 / 0.05 dm3 • Equals 0.5 mol / dm3

  12. Ultra Fun Worksheet • Complete the ultra fun worksheet • If you finish early, get started on this: • Acids & Alkalis Page 44-45 (Questions 1-6)

  13. Don’t Be Too Acidic • One important type of chemicals are called acids. • Examples include: Sulfuric Acid (H2SO4), Vinegar (CH3COOH), Hydrochloric Acid (HCl) and Nitric Acid (HNO3) • Acids are solutions of pure compounds in water • They are corrosive, especially if they have a high molar value • Some acids are strong for the same molar value (eg Sulfuric Acid), but some are weaker (Vinegar or Ethanoic Acid)

  14. Acids #2 • Acids can be tested in different ways. The 2 main ways we will learn are: • Litmus Solution. This solution is purple and will turn red if an acid • Litmus Paper. The paper is blue and will turn red if an acid. • Acids are reactive as they often have a Hydrogen atom that can be removed easily.

  15. Interesting But Don’t Need To Know • When an acidic compound loses an Hydrogen atom, they dissociate an Hydrogen atom. • Some acids like Phosphoric Acid can lose up to 3 hydrogen atoms (H3PO4).

  16. AlkaAlkaAlkali • Another important type of chemical is called alkalis. • They need to be handled carefully as they often can burn the skin if strong. • Examples of Alkali solutions include: Sodium Hydroxide (NaOH), Potassium Hydroxide (KOH) and Ammonia Solution (NH3) • Alkali’s turn red litmus solution blue, and red litmus paper blue

  17. Neutral Substances • Some substances are not classed as acids or bases, as they do not affect litmus paper. • Examples include Salt (NaCl) and Sugar solutions.

  18. pH Scale • The pH scale measures how many hydrogen (H+) atoms are present in water. • If it is acidic, there are more H+ atoms. These are also described as H3O+ or hydronium ions. • If it is basic, there are more OH- compounds. This is often called Hydroxide.

  19. Continued • An acidic solution has a pH less than 7 • An neutral solution has a pH of 7 • An alkaline (or basic) solution has a pH higher than 7

  20. Questions • To be completed at end of class or for homework. • Read Page 44/45 and answer Q 1-6 • Next lesson – titrations of CC Lemon!!

More Related