Identification of a Compound using Melting and Boiling Points

Introduction

Data & Results

Table One – Experimental Data 

Trial	Water Melting Pt.	Water Boiling Pt.	Unknown 7 Melting Pt.	Unknown 7 Boiling Pt.
1	0.7 °C  *	101.2 °C	80.2 °C	272.7 °C
2	0.1 °C	101.1 °C	80.7 °C	272.8 °C
3	0.0 °C	100.9 °C	80.4 °C	273.0 °C
4	0.1 °C	n/a	n/a	n/a
Averages:	0.15 °C	101.1 °C	80.4 °C	272.8  °C
Standard deviation (s):	± 0.06	± 0.15	± 0.15	± 0.06
95% confidence limits:	± 0.14	± 0.4	± 0.4	± 0.14

Table Two – Corrected Temperatures  

	Unknown 7 Melting Pt.	Unknown 7 Boiling Pt.
Measured value	80.4 °C ± 0.4 (95%)	272.80 ± 0.14 °C (95%)
Correction	+0.15 °C	+ 1.1 °C
Corrected value	80.5 °C ± 0.4 (95%)	273.90 ± 0.14 °C (95%)

Table Three – Reference Data from Chemical Handbook 

Compound	Melting Point	Boiling Point
Blabber Gas	-15.8 °C	17.2 °C
Freezer Gel	82.7 °C	456.1 °C
Silly Putty	57.2 °C	121 °C
Billgatesium	1000 °C	unknown
Farsel Juice	80.8 °C	274.0 °C
Shampoo	-1.2 °C	108.7 °C

 

Stoichiometry

The quantitative relationship among reactants and products is called stoichiometry. The term stoichiometry is derived from two Greek words: stoicheion (meaning "element") and metron (meaning "measure"). On this subject, you often are required to calculate quantities of reactants or products.

Stoichiometry calculations are based on the fact that atoms are conserved. They cannot be destroyed or created. Numbers and kinds of atoms before and after the reactions are always the same. This is the basic law of nature.

From the atomic and molecular point of view, the stoichiometry in a chemical reaction is very simple. However, atoms of different elements and molecules of different substances have different weights. Thus, simple stoichiometry at the atomic level appears to be complicated when amounts (quantities) are measured in units of g, kg, L or mL. When quantities in moles are used, the relationships (or ratios) are really simple. For example, one mole of oxygen reacts with two moles of hydrogen,
2 H2 + O2 -> 2 H2O
or one mole of hydrogen reacts with half a mole of oxygen,
H2 + ½ O2 -> H2O
one mole of carbon reacts with one mole of oxygen.
C + O2 -> CO2

This is a major and important topic that you have to master. In order to accomplish this, you have to be able to do several things. First, you have to be able to convert amounts of substances between mass units of g (or kg) to moles and vice versa. Then, you have to understand chemical reactions (changes). In this case, you not only know what are the reactants and products, you can write a balanced equation to explain the reaction. Sometimes you may be told what the reactions are.

There are many chemical reactions, but they can be divided into a few types as a summary.

In a chemical reaction, not all reactants are necessarily consumed. One of the reactants may be in excess and the other may be limited. The reactant that is completely consumed is called limiting reactant, whereas unreacted reactants are called excess reactants.

Amounts of substances produced are called yields. The amounts calculated according to stoichiometry are called theoretical yields whereas the actual amounts are called actual yields. The actual yields are often expressed in percentage, and they are often called percent yields.

Problems  

1.    Mole-Mole Problems
Problem:  How many moles of HCl are needed to react with 0.87 moles of Al?

        Step 1: Balance The Equation & Calculate the Ratios


            2Al:6HCl (1:3)        2Al:2AlCl₃ (1:1)        2Al:3H₂ (1:1.5)
        Step 2:  Find the Moles of the Given             0.87 moles of aluminum are reacted with hydrochloric acid
          Step 3: Calculate the moles using the ratios            moles HCl = 0.87molAl x  3molHCl/1molAl = 2.6 mol HCl
           

2.    Mass-Mass Problems (Strategy: Mass g Mole g Mole g Mass)
Problem:  How many grams of Al can be created decomposing 9.8g of  Al₂O₃?

        Step 1: Balance The Equation & Calculate the Ratios  

            2Al₂O₃:4Al (1:2)        2Al₂O₃:3O₂ (1:1.5)

Step 2:  Find the Mass of the Given

            9.8g Al₂O₃ are decomposed

Step 3: Calculate the moles of the given (mol/g)

            9.8g Al₂O₃ x (1mol Al₂O₃/102g Al₂O₃) = 0.096 mol Al₂O₃
       

Step 4: Calculate the moles using the ratios

        0.096 mol Al₂O₃ x (2 mol Al/1 mol Al₂O₃) = 0.19 mol Al
      
        Step 5: Calculate the mass using the new moles
        0.19 mol Al x (27g Al/1 mol Al) = 5.1g Al
       

3.    Mass-Volume Problems (Strategy: Mass g Mole g Mole g Volume)
        Problem:  How many liters of H2 are created from the reaction of 20.0g K?

        Step 1: Balance The Equation & Calculate the Ratios



            2K:2H₂O (1:1)    2K:2KOH (1:1)    2K:1H₂ (2:1)

Step 2:  Find the Mass of the Given

            20.0g K are used in the reaction

Step 3: Calculate the moles of the given (mol/g)

            20.0g K x (1 mol K / 39g K) = 0.513 mol K
           

Step 4: Calculate the moles using the ratios

            0.51 mol K x (1mol H₂ /2mol K) = 0.266mol H₂
           
        Step 5: Calculate the volume using the new moles
        0.266 mol H₂ x (22.4L H₂ /1mol H₂) = 5.75L H₂
       

4.    Volume-Volume Problems
        Problem:  How many liters of SO₂ will be produced from 26.9L O₂?

Step 1: Balance The Equation & Calculate the Ratios

            2O₂:1S₂ (2:1)    2O₂:2SO₂ (1:1)

Step 2: Find the volume of the given

            26.9L O₂

Step 3: Calculate the moles of the given

            26.9L O₂ x (1 mol O₂ / 22.4L) = 1.20 mol O₂
       

Step 4: Calculate the moles using the ratios

            1.20 mol O₂ x (1mol SO₂ /1mol  O₂) = 1.20 mol SO₂
       
        Step 5: Calculate the volume using the new moles
        1.20 mol O₂ x (1mol SO₂ /1mol  O₂) x (22.4L /1mol) = 26.9L SO₂
       

Chemistry happens in the world around you, not just in a lab. Matter interacts to form new products through a process called a chemical reaction or chemical change. Every time you cook or clean, it's chemistry in action. Your body lives and grows thanks to chemical reactions. There are reactions when you take medications, light a match, and take a breath. Here's a look at 10 chemical reactions in everyday life. It's only a small sampling since you see and experience hundreds of thousands of reactions each day.

1.Photosynthesis Is a Reaction To Make Food

                                                   Photoynthesis Chlorophyll in plant leaves converts carbon dioxide and water into glucose and oxygen.

Plants apply a chemical reaction called photosynthesis to convert carbon dioxide and water into food (glucose) and oxygen. It's one of the most common everyday chemical reactions and also one of the most important since this is how plants produce food for themselves and animals and convert carbon dioxide into oxygen.

6 CO2 + 6 H2O + light → C6H12O6 + 6 O2

2.Aerobic Cellular Respiration Is a Reaction With Oxygen

Aerobic cellular respiration is the opposite process of photosynthesis in that energy molecules are combined with ​the oxygen we breathe to release energy needed by our cells plus carbon dioxide and water. Energy used by cells is chemical energy in the form of ATP.

Here is the overall equation for aerobic cellular respiration:

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (36 ATPs)

3.Anaerobic Respiration - Everyday Chemical Reactions

In contrast to aerobic respiration, anaerobic respiration describes a set of chemical reactions that allow cells to gain energy from complex molecules without oxygen. Your muscles cells perform anaerobic respiration whenever you exhaust the oxygen being delivered to them, such as during intense or prolonged exercise. Anaerobic respiration by yeast and bacteria is harnessed for fermentation, to produce ethanol, carbon dioxide, and other chemicals that make cheese, wine, beer, yogurt, bread, and many other common products.

The overall chemical equation for one form of anaerobic respiration is:

C6H12O6 → 2C2H5OH + 2CO2 + energy

4.Combustion Is a Type of Chemical Reaction

                                               Combustion is a chemical reaction in everyday life. WIN-Initiative / Getty Images

Every time you strike a match, burn a candle, build a fire, or light a grill, you see the combustion reaction. Combustion combines energetic molecules with oxygen to produce carbon dioxide and water.

For example, the combustion reaction of propane, found in gas grills and some fireplaces, is:

C3H8 + 5O2 → 4H2O + 3CO2 + energy

5.Rust Is a Common Chemical Reaction

Over time, iron develops a red, flaky coating called rust. This is an example of an oxidation reaction. Other everyday examples include formation of verdigris on copper and tarnishing of silver.

Here is the chemical equation for the rusting of iron:

Fe + O2 + H2O → Fe2O3. XH2O

6.Mixing Chemicals Causes Chemical Reactions

 
Baking Powder and baking soda perform similar functions during baking, but they react differently with the other ingredients so you can't always substitute one for the other. Nicki Dugan Pogue / Flickr / CC BY-SA 2.0
If you combine vinegar and baking soda for a chemical volcano or milk with baking powder in a recipe you experience a double displacement or metathesis reaction (plus some others). The ingredients recombine to produce carbon dioxide gas and water. The carbon dioxide forms bubbles in the volcano and helps baked goods rise.

These reactions seem simple in practice but often consist of multiple steps. Here is the overall chemical equation for the reaction between baking soda and vinegar:

HC2H3O2(aq) + NaHCO3(aq)  → NaC2H3O2(aq) + H2O() + CO2(g)

7.Batteries Are Examples of Electrochemistry

Batteries use electrochemical or redox reactions to convert chemical energy into electrical energy. Spontaneous redox reactions occur in galvanic cells, while nonspontaneous chemical reactions take place in electrolytic cells.

8.Digestion- Everyday Chemical Reactions

 
                                                                                       Peter Dazeley/Photographer's Choice/Getty Images

Thousands of chemical reactions take place during digestion. As soon as you put food in your mouth, an enzyme in your saliva called amylase starts to break down sugars and other carbohydrates into simpler forms your body can absorb. Hydrochloric acid in your stomach reacts with food to break it down, while enzymes cleave proteins and fats so they can be absorbed into your bloodstream through the walls of the intestines.

9.Acid-Base Reactions- Everyday Chemical Reaction

                                               When you combine and acid and a base, salt is formed. Lumina Imaging/Getty Images

Whenever you combine an acid (e.g., vinegar, lemon juice, sulfuric acid, muriatic acid) with a base (e.g., baking soda, soap, ammonia, acetone), you are performing an acid-base reaction. These reactions neutralize the acid and base to yield salt and water.

Sodium chloride is not the only salt that may be formed. For example, here is the chemical equation for an acid-base reaction that produces potassium chloride, a common table salt substitute:

HCl + KOH → KCl + H2O

10.Soaps and Detergents - Everyday Chemical Reactions

                                                                                                        JGI/Jamie Grill/Getty Images

Soaps and detergents clean by way of chemical reactions. Soap emulsifies grime, which means oily stains bind to the soap so they can be lifted away with water. Detergents act as surfactants, lowering the surface tension of water so it can interact with oils, isolate them, and rinse them away.

The diagram of an atom is among the most familiar symbols of science there is. Unfortunately, it's not actually what atoms look like, and we've known that for nearly a century.

How The Diagram Came To Be

The history of the atomic model is long—we could go back as far as the ancient Greeks, really—but for our purposes, we can start around 1900. It was about then that Sir Joseph John Thomson discovered the electron, which is the negatively charged part of an atom. He proposed that these electrons were captured in uniform spheres of positively charged matter. This was dubbed the "plum-pudding model," since the electrons in the positive substance is a bit like plums in English pudding. New Zealand physicist Ernest Rutherford discovered that if you shoot positive particles at atoms (in the form of gold foil), they don't all bounce off the way they should if there was a large mass of positive "pudding." Instead, some bounce off, but most pass through, suggesting that electrons are spaced around a small mass of positive substance—a nucleus, if you will. He rejiggered the model in 1911 to have electrons orbiting a nucleus the way that planets orbit the sun, which was dubbed the "planetary model," for obvious reasons. The planetary model has become the most famous symbol for the atom—even though it was refined only two years later by Danish physicist Niels Bohr.

 The problem with the planetary model is that electrons would lose energy by orbiting, causing them to collapse into the nucleus. Bohr's model solved this: instead of orbiting willy nilly, electrons orbited only at very specific energy levels. Electrons could jump from level to level if they absorbed or released energy, but they never drifted between levels. The Bohr model is probably the most popular in science textbooks (you'd recognize it as a nucleus surrounded by ever larger circles of electrons) but—you guessed it—it's mostly wrong, too.

What's Really Going On?

Steven Dutch of the University of Wisconsin Green Bay clearly sums up the next step in the atomic model: "By the 1920's, physicists had discovered that matter also has wave-like properties and that it just doesn't work at the atomic level to regard particles as tiny points with precise locations and energies. Matter is inherently 'fuzzy.' They gave up thinking of electrons as tiny planets altogether." Electrons don't really follow paths at all. Physicists discovered that they're actually quantum particles that exist in many different places at once. They still occupy individual energy levels, but instead of a path, each electron's many-places-at-once location could be thought of as a cloud. That's why it's known as the electron cloud model.
   That's not to say Bohr was wrong. It's a good way to simplify a very complicated concept, and it actually works surprisingly well for simple atoms like hydrogen. But the electron cloud model illustrates the latest knowledge about the structure of an atom. The planetary model is pretty, but reality it ain't.

Located inside the Fundació Joan Miró in Barcelona, Calder’s Mercury fountain is one of the deadliest works of art in existence today. Donated to the foundation by the artist himself, the fountain is kept behind a glass casing to protect visitors from the highly toxic substance that gives the monument its most unique character. This is the story of how this deadly masterpiece came to be the world’s most famous mercury fountain to date.

Of course, what wasn’t understood back then is that mercury is in fact highly toxic and mercury poisoning can lead to sensory impairment, a feeling of itching and burning and ultimately, death. The expression ‘as mad as a hatter’ appeared in the 19th century owing to the odd behaviour frequently noticed in those who worked in the hatmaking industry – a profession which used mercury in the manufacturing process. However the discovery of mercury’s toxicity in the human body was a lengthy process and it wasn’t until the mid 20th century that scientists concurred on the dangers of exposure to mercury.

The element’s unique physical properties meant that it was frequently used in science and technology, especially in electronics. In the early 20th century mercury mining was a lucrative business and demand for the metal was high. At that moment in time one of the largest mercury mines in the world was that of the Spanish town of Almadén, which is thought to have supplied about 60% of the world’s mercury.
 In 1936 the three-year Spanish civil war broke out, pitting supporters of the Republican government against supporters of General Franco’s Falangist movement – the latter would come out victorious in 1939, marking the beginning of the dictatorship which would last until 1975. During the height of the civil war, Franco’s troops launched an attack on the town of Almadén and besieged the mercury mine – a costly move for the Spanish government who was deprived of the financial revenues from the export of mercury, as well as access to the metal which was used in the creation of firearms.

 It was in this context that in 1937, struggling to retake control of the city, that the Republican government commissioned the artist Alexander Calder to create a monument denouncing the siege of Almadén to be presented at the 1937 World Exhibition in Paris. This wasn’t the only notable art work to be commissioned by the government for the occasion, the other being Pablo Picasso’s world-famous Guernica painting.
 Today the fountain is located within the Joan Miró Foundation on Montjuïc hill in Barcelona – donated to the museum by the artist himself – where it lies behind a glass casing designed to protect visitors from the poisonous fumes which emanate from the fountain. Few who visit the monument are aware of the historic struggle from which the piece originates. A mesmerisingly beautiful, yet lethal reminder of Spain’s troubled past and the brutality of a war whose legacy continues to resonate in the country today.

The application of a scientific approach will be the challenge of teachers through the development of 7 activities of students that is observing, asking, trying, processing, tasting, reasoning, and creating.

The Dialogue:
 On thursday morning chemistry class prepare the references to study about acid,base and the pH
before the the teacher comes.
*teacher enter the class*

Teacher : Good morning everybody, in this morning we will discuss about acid and bases and pH . So who know the Defenition of Acid And Bases?

Student : *hand’s up* I know sir

Teacher : Yes, please

Student : Acids are ionic compounds that produce positively charged hydrogen ions (H+)  when dissolved in water. Acids taste sour and react with metals. Bases are ionic compounds that produce negatively charged hydroxide ions (OH-) when dissolved in water. Bases taste bitter and do not react with metals. Examples of acids are vinegar and battery acid. The acid in vinegar is weak enough to safely eat on a salad. The acid in a car battery is strong enough to eat through skin. Examples of bases include those in antacid tablets and drain cleaner. Bases in antacid tablets are weak enough to take for an upset stomach. Bases in drain cleaner are strong enough to cause serious burns.

Teacher : Ok, that’s good. So Acids are ionic compounds that produce positively charged hydrogen ions (H+) when dissolved in water. Acids taste sour and react with metals. Bases are ionic compounds that produce negatively charged hydroxide ions (OH-) when dissolved in water.Understand?

Student : *hand’s up* sir, What do you think causes these differences in the strength of acids and bases?
Teacher : The strength of an acid or a base depends on how much of it breaks down into ions when it dissolves in water
 
Student : *hand’s up* What determines how acidic or basic a solution is??

Teacher : Acidic solutions have a high concentration of H+, and those that are basic will have a low H+ concentration and a higher OH- concentration.Thus the higher the concetration of protons, the lower the ph will be. The same is true for alkaline solutions which have a high ph. Any other questions?

Student : What is pH? What is the pH of a neutral substance?

Teacher : The strength of acids and bases is measured on a scale called the pH scale. By definition, pH represents the acidity, or hydrogen ion (H+) concentration, of a solution. Pure water, which is neutral, has a pH of 7. With a higher the concentration of hydrogen ions, a solution is more acidic and has a lower pH. Acids have a pH less than 7, and the strongest acids have a pH close to zero. Bases have a pH greater than 7, and the strongest bases have a pH close to 14. Got it?

Student : How much more acidic is a solution with a pH of 4 than a solution with a pH of 7??

Teacher : A solution with a pH of 4 is 1000 (10 × 10 × 10, or 103) times more acidic than a solution with a pH of 7..

Student : *hand’s up* Why is the pH of the environment important for living things??

Teacher : Acidity is an important factor for living things. For example, many plants grow best in soil that has a pH between 6 and 7. Fish may also need a pH between 6 and 7. Certain air pollutants form acids when dissolved in water droplets in the air. This results in acid fog and acid rain, which may have a pH of 4 or even lower
*the bells are ringing*
Teacher : Ok, I think It’s enough for today. See you on the next lesson and don’t forget to prepare the references about Rate of law for next week.

All of students : Ok sir!