SNC 2P - Chemistry - Acid Rain

What is acid rain?  Let's find out.

How does acid rain affect you?  Let's find out. 

 

Acid Rain Reading Assignment

 

This reading is from a pamphlet, so the order to read it is a bit odd.  Read the section between the arrows on the first page.  As for the second and third pages, they were originally like a centrefold.  So, read across the top of the second page, then the top of the third page, then the bottom of the second page and finally the bottom of the third page.  Whew!!

 

Answer all questions in full sentences.  Turn in your work on Edsby by 2:15 today.

SNC 2P - Chemistry - Acid-Base Neutralization Reaction

Acid-Base Neutralization

Acids and bases, when combined together in equivalent amounts, will neutralize each other.

This reaction is called an acid-base neutralization reaction or simply, a neutralization reaction.

A neutralization is a special example of a double replacement reaction:

Acid     +     Base     →     a Salt     +     Water

hydrochloric acid + sodium hydroxide → sodium chloride + water

HCl     +     NaOH     →     NaCl     +     H₂O

 

Want to see the above neutralization reaction being carried out in a lab?  Click here.

 

Question of the Day #16:

Read p. 167.  Choose a profession and answer the following questions: 

1.  What profession did you choose?

2.  What dangers does this profession face?

3.  What precautions can be taken to reduce the risk?

Spoiler Alert!

Here's a little intro for tomorrow's lesson.  Here's a bit more goodness. 

SNC 2P - Chemistry - pH Scale

The acidity or basicity of a substance can be indicated using an indicator’s colour change or by using numbers.

The pH scale is a sequence of numbers ranging from 0 to 14 (although it is possible to have a pH lower than 0 or greater than 14).  The pH value is a indication of hydrogen ion (H+) concentration. 

• Lower numbers (0 to just before 7) indicate an acidic substance.
• Higher numbers (just above 7 to 14) indicate a basic substance.
• Exactly 7 indicates a neutral substance (which is neither acidic nor basic).

 

Check out this video, for some more pHantastic chemistry! 

The term "pH" stands for "power of hydrogen," since an increase (or decrease) of pH by 1, represents a ten-fold change in hydrogen ion concentration.  Thus, small changes in pH relates to large changes in acidity or basicity strength.  

Each time the pH value changes by one, the strength of the acid or base changes by ten times.  For example, an substance with a pH of 2 is ten times more acidic than a substance with a pH of 3.

Environmental scientists are very concerned about changes in pH when in comes to bodies of water on Earth.  Let's find out why.

Now, let's make like a referee and get neutral.

 

SNC 2P - Chemistry - Acids & Bases

Acids

Acids are found in many substances we use on a daily basis, like lemons and other citrus fruits, vinegar, grapefruit and  milk.

Although foods that contain acids are safe to eat, not all substances that contain acid should be eaten.

Many acids are corrosive and this makes them dangerous to eat or have on your skin, as the acid will “eat away” at your tissues.

Acids are substances that increase the concentration of hydrogen ions (H+) when placed in aqueous solution. 

They have the general formula HX, where X represents an anion.

What are the strongest acids in the world, you may ask?

 

 

Bases

Bases are also found in many substances that we use on a daily basis, like antacids, tonic water, baking soda and bittersweet chocolate.

Bases can also be dangerous and corrosive, so caution is often required.

Bases are substances that increase the concentration of hydroxide ions (OH-) when placed in aqueous solution.

They have the general formula MOH, where M usually represents a metal ion.

Let's check out this video for some more acid and base love.

 

Indicators

Indicators are used to indicate the acidity or basicity of a substance by a change in colour.

Some common ones are phenolphthalein, bromthymol blue, litmus paper.

Want to make your own acid-base indicator?  Stay tuned.

Check out the cool way this high school student has used the colour changing properties of indicators to make a difference in the world.  Wow!

 

Homework:

Use the internet to find the answers for the following chart.

 

 

SNC 2P - Chemistry - Double Replacement Reactions

Double replacement reactions involve the swapping of elements between two different compounds.

The general formula is: 

WX     +      YZ     →     WZ     +     YX

or  

compound + compound → new compound + new compound

This is analogous to two dancing couples switching partners,

 

Some lone elements are “special” and will be found as diatomics or polyatomics: H₂, O₂, N₂, F₂, Cl₂, Br₂, I₂, P₄, S_8.

All other elements are monatomics:  Fe, Ca, Li, etc.

Remember:  Elements combined in compounds use their valances to determined the ratios in a compound.

 

Practice Questions:

For each of the following (a) complete the word equation, (b) create a balanced equation.

(a) barium iodide + silver sulfide  →

(b)  sodium chloride + tin (II) bromide   →

(c)  lead (II) sulfide + aluminum fluoride   →

 

Answers:

(a) barium iodide + silver sulfide → barium sulfide + silver iodide

             BaI₂        +      2AgS       →        2BaS        +     Ag₂S

(b) sodium chloride + tin (II) bromide → tin(II) chloride + sodium bromide

            2NaCl          +       SnBr₂        →         SnCl₂      +     2NaBr

 

(c) lead (II) sulfide + aluminum fluoride → aluminum sulfide + lead (II) fluoride

           3PbS          +          2AlF₃           →           Al₂S₃         +       3PbF₂

 

Homework:

Answers: