Covalent bonding
Covalent bonding is an intermolecular form of chemical bonding characterized by the sharing of one or more pairs of electrons between two components, producing a mutual attraction that holds the resultant molecule together. Atoms tend to share electrons in such a way that their outer electron shells are filled - this is referred to as electron configuration. Such bonds are always stronger than the intermolecular hydrogen bond and similar in strength to or stronger than the ionic bond. In contrast to the ionic and metallic bond, the covalent bond is directional, i.e. the bond angles have a great impact on the strength of the bond. Because of the directional character of the bond, covalently bound materials are more difficult to deform than metals. The cause of the directionality is the form of the s, p, d, and f orbitals. In organic chemistry, the directionality of the bonding is often described by hybrid orbitals. Covalent bonding most frequently occurs between atoms with similar electronegativities. For this reason, non-metals tend to engage in covalent bonding more readily since metals have access to metallic bonding, where the easily-removed electrons are more free to roam about. For non-metals, liberating an electron is more difficult, so sharing is the only option when confronted with another species of similar electronegativity. However, covalent bonding involving
Purity of egg shell
Purity of egg shell Name: Ismaila Neill Aim: To find the percentage purity of an eggshell Apparatus and materials: * Filter paper * Spatula * Eggshell * Electrical balance * Filter paper * 100cm3 beaker * Dilute hydrochloric acid (HCl) * Pestle and mortar * 100cm3 measuring cylinder * Glass rod Procedure: . White inner lining of eggshell is carefully removed 2. Egg shell is placed on dry filter paper and mass is recorded using Electronic balance 3. Eggshell is broken up into small pieces using pestle and mortar 4. 50cm3 of hydrochloric acid is added to beaker with eggshell and stirred with glass rod 5. Stirring is continued until eggshells stop producing bubbles indicating that no more eggshell can be dissolved 6. Mixture is filtered for a day and the residue of eggshell is left in filter paper 7. Residue is left to dry ,and the mass of the filtrate along with the residue and dry filter paper is recorded 8. The residue is removed and the mass of the filter paper is recorded. Results Mass of eggshell=27.55g Mass of filter paper + egg-shell residue= 15.6g Mass of filter paper without residue=2.06g Calculations 1. Mass of residue= (mass of filter paper + residue)-(mass of dry filter paper) =15.6-2.06 =13.14g 2. Mass of calcium carbonate= (Initial mass of eggshell)-(mass of residue) =27.55-13.14 =14.41g 3. Percentage purity of egg shell= =
The rates of reaction between CaCO3 and HCL
March 2004 SC1: Chemistry Course work 1 Background information * CaCO3 + 2HCl CaCl + H2O + CO2 * The rate of reaction is affect by: Temperature, Surface area, Volume of HCL, Mass of CaCO3 * The higher the average decrease, in mass, the higher the purity * The ratio of reactions needs to be unbalanced, there needs to be twice the amount of HCL than the mass of CaCO3 * 100g of pure CaCO3 yields 44g of CO2 Problem Two samples of Limestone have been quarried from different points of a quarry (East and West) these need to be tested to see which the purist is. Preliminary Investigation: In mass of CaCO3 and HCL need to be decided to do this I will set up two experiments using: * Conical flasks * Stop Clock * Balance * Spatula * Measuring flask * Powered Limestone * Hydrochloric acid Diagram to show set up of apparatus The two experiments need to test the ratio of reactions this is done my measuring amounts of CaCO3 in to a Conceal Flask adding acid and writing down the change of mass of a set range at certain intervals. The ratio of reactions needs to be unevenly balanced double the amount of HCL to CaCO3 if the reactions are balanced the experiment will not work, if there is to little HCL then there will be CaCO3 left in the flask at the end of the experiment. Method: I set up a conical flask on a balance, with a reading of 0.00, and then
investigation of properties of a pair of cis, trans isomers
TAS experiment No 18 (Chung Pui Wu) . Date 2. Title Investigation of properties of a pair of cis, trans isomers 3. Objective Determine the percentage yield of fumaric acid. Compare the properties, like solubility in water , acid strength and reaction with acidified potassium permanganate, of the cis and trans isomers (maleic acid and fumaric acid). 4. Introduction Butenedioic acid, C4H4O4, exists as two distinct geometrical isomers: These two isomers of butenedioic acid are commonly known as maleic acid and fumaric acid (not necessarily in that order). Each of them has its own distinctive properties such as melting point, solubility in water, density and stability. In this experiment you will convert some maleic acid to fumaric acid by heating in an aqueous solution containing some hydrochloric acid, which serves as a catalyst. You will then compare the properties of these two isomers and use the results to identify which isomer is maleic acid and which isomer is fumaric acid. 5. Procedure Day 1 Part A - Conversion of maleic acid to fumaric acid 1. Weigh out about 4g of maleic acid in a clean, dry 100cm3 beaker. Record the mass accurately. 2. Add about 15cm3 of distilled water to beaker. Warm the mixture slightly to dissolve the acid completely. 3. Add about 10cm3 of concentrated hydrochloric acid to the beaker, and cover it with a
Plastics Friend or Foe
PLASTICS - FRIEND OR FOE In the modern age, the use of plastics has caused a heated discussion amongst many parties. Politicians, environmentalists, the media, corporations, the general public etc. have argued for and against the use of plastics. This assignment will look into the importance of plastics in our society and the damage that it causes. The first type of plastic manufactured for people to use was created in 1863 by an inventor called John Hyatt, but it wasn't until the 1930s did scientists gained a better understanding of developing plastics through crude oil, gas and other natural hydrocarbons. Technologies further improved during WW2 and the 1950s which drove the development of most plastics we see today. Nowadays, plastics play an incredibly important part of our lives. The majority of the things we own or use will consist of plastic. The two biggest reasons for its popularity are its usefulness and economic value. Plastic is a material that can provide consumers with their needs and wants. It has the unique capability to be manufactured to meet very specific functional needs for consumers. Listed are some key features that make plastic the material of choice for most producers. VERSATILITY One of the biggest assets of plastic is that it can be manufactured to use in almost any shape or form. It can be shaped using heat and once cooled, it will remain in
material science unit 2 task 2
Types of materials Metals and alloys: iron, copper, aluminium, steel. Structure of metals: The atoms in metals are closely packed; they fit as many atoms as they can in one bulk of metal. Each atom is attached to 6 other atoms in its outer layer e.g. Composition: Metals are composed of atoms and in those atoms there are Electrons, Protons and Neutrons, in every atom there usually are the same number of neutrons and electrons, but the numbers of protons differ as some atoms have one more proton then electrons and neutrons. E.g. iron Properties: Chemical properties: They have 1-4 atoms in their outer shell. They loose electrons easily (low ionisation potential) They give away their electrons easily (reducing agents) They have hydroxides that react as both weak acids and bases (amphoteric). They have the tendency to loose electrons than gain them. (Electropositive). 82 elements in the periodic table may be classed as metals. Physical properties . They have a metallic shine 2. They diffuse light. 3. Excellent conductors of heat and electricity 4. Very strong 5. Dense - heavy for their size 6. Pliable and ductile (high plasticity) they can be made in to thin wires or hammered in to thin sheets of metals. 7. Resistant to fracture, not easy to break 8. Atoms are arranged in a constant structure. 9. High
The discovery of the elements.
Open Book Paper 'The nineteenth century was a golden age for the discovery of elements [1]'. This was when scientist began to look for patterns and behaviours of elements. The early periodic table was arranged by the elements relative atomic mass rather than atomic number, which is now seen in the modern periodic table. Johann Dobereiner was the first to attempt to classify elements using their RAM (relative atomic mass). He identified that in a set of three elements (then known) in a group have similar properties (e.g. Cl, Sr and Ba [1]). He calculated that the RAM of the middle element is approximately the average of the other two elements (this was before the discovery of the noble gases). But after 20 elements his table became ragged and incorrect because he had to put two elements in one space and the RAM values were incorrectly measured. It was in 1869 when Russian chemist Dimitri Mendeleev had produced a better version of the table (see below). He altered some of the RAM values and left gaps for undiscovered elements. The gaps were a prediction for new elements and were taken as a bold policy by other scientists because if proven wrong, his explanation* will fail. [4] The discovery of gallium by the French scientist, Paul. E. L. de Boisbaudran supported Mendeleev's ideas about the periodic table because gallium fitted into one of the gaps he had left for
Determination of the formula of hydrated iron sulphate
Determination of the formula of hydrated iron sulphate Analysis Method 1 Results Mass of iron sulphate before heating .372 Mass of iron sulphate after heating the 1st time 0.698 Mass of iron sulphate after heating the 2nd time 0.718 Mass of iron sulphate after heating the 3rd time 0.720 Mass of iron sulphate after heating the 2nd time 0.720 Final mass of iron sulphate after heating 0.720 The mass of FeSO4. xH2O I weighed out to begin was 1.372g. After heating the mass was 0.720g. Having heated the FeSO4. xH2O all of the water has evaporated out so the mass that I am left with is the mass of FeSO4 which was 0.72 g. The mass of the H2O can then be calculated by subtracting the mass of FeSO4 from the mass of FeSO4. xH2O. Therefore; Mass of H2O = Mass of FeSO4. xH2O - Mass of FeSO4 Mass of H2O = 1.372 - 0.72 Mass of H2O = 0.652g So I now know both the mass of H2O and the mass of FeSO4 . This means that I can calculate the number of moles for both FeSO4 and H2O To calculate these I will use the equation: Moles of FeSO4 = mass Mr Moles of FeSO4 = 0.72 55.9 + 32.1 + (16 x 4) Moles of FeSO4 = 0.004736842 This value quoted for moles of FeSO4 is quoted to higher degree of accuracy than I could calculate so Instead I will quote this value to 3 significant figures. Therefore: Moles of FeSO4 = 0.00474 correct to 3 significant
It is is more important to pray privately than to the celebrate the Eucharist - Do you agree? Give reasons for your answer, showing you have thought about more than one point of view.
RE COURSEWORK Question 6: "Its is more important to pray privately than to the celebrate the Eucharist." Do you agree? Give reasons for your answer, showing you have thought about more than one point of view. Prayer is an important way of communicating with God. It is a way of thanking him for what he has done and what he is doing. It is also a way of asking for help. It is crucial to pray when you are a Christian, whether you are alone or as a group. When praying privately it is more intimate than going to mass, you can concentrate your mind better and ask for Gods forgiveness and needs more easily on a one to one basis. The atmosphere created is more peaceful, relaxed and calm, leading to a clear mind, taking you on an inward journey. Praying privately means you can you do it by yourself in any place at any time so doing it in your own home can make it more comfortable for you to express your feelings to God. It is up to you and therefore helps to build a strong personal relationship between you and God by expressing you innermost feelings. Jesus prayed in private on at least three occasions. He was sent for us to follow and therefore we should also follow him in praying privately. He constantly turned to his father for help asking for strength and encouragement throughout his life, therefore we should do the same. However, the Eucharist is the highest form of prayer
Chemistry revision notes. Atomic Structure and Bonding, Electrolysis, Acids and Alkalis.
Atomic Structure and Bonding (F) Atoms, Molecules and Ions. AN ATOM is the smallest particle of an element. They cannot be split into smaller particles in chemical reactions. Iron is made of iron atoms (Fe). Sulphur is made of sulphur atoms (S) A MOLECULE is a small group of atoms joined together. The atoms may be the same (e.g. O2) or different (e.g. H2O). The chemical formula shows the number and type of atoms present. Non-metal compounds are made of molecules: Carbon dioxide contains CO2 molecules Methane (natural gas) contains CH4 molecules AN ION is an atom or group of atoms with an electrical charge (+ or -). Metal compounds such as sodium chloride or copper sulphate contain ions. Sodium chloride is made of Na+ and Cl- ions Magnesium Oxide is made of Mg2+ and O2- ions Note that metals form positive ions while non-metals form negative ions. A solid is represented by (s). e.g. H2O(s) is ice. A liquid is represented by (l) e.g. Fe(l) is molten iron. A gas is represented by (g) e.g. H2O(g) is steam. A solution in water is represented by (aq). Salt dissolved in water is NaCl(aq). You should remember that the common gases are diatomic (have 2 atoms in each molecule). These are Oxygen O2; Hydrogen H2; Nitrogen N2; and Chlorine Cl2. Elementary Particles Atoms are made up of smaller particles called protons, neutrons and electrons. The protons and neutrons
