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Chemistry Applications

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1st Diploma Applied Science Unit 3 - Chemistry Applications Assignment no. 1 1. Know how atomic structure relates to the properties of the elements and compounds 2. Understand the factors involved in chemical reactions. Task 1 1.a No. Symbol of element Element Atomic structure Electronic configuration 1 H Hydrogen 1 p+ ; 0 n0 ; 1 e- 1 2 He Helium 2 p+ ; 2 n0 ; 2 e- 2 3 Li Lithium 3 p+ ; 4 n0 ; 3 e- 2, 1 4 Be Beryllium 4 p+ ; 5 n0 ; 4 e- 2, 2 5 B Boron 5 p+ ; 6 n0 ; 5 e- 2, 3 6 C Carbon 6 p+ ; 6 n0 ; 6 e- 2, 4 7 N Nitrogen 7 p+ ; 7 n0 ; 7 e- 2, 5 8 O Oxygen 8 p+ ; 8 n0 ; 8 e- 2, 6 9 F Fluorine 9 p+ ; 10 n0 ; 9 e- 2, 7 10 Ne Neon 10 p+ ; 10 n0 ; 10 e- 2,8 11 Na Sodium 11 p+ ; 12 n0 ; 11 e- 2, 8, 1 12 Mg Magnesium 12 p+ ; 12 n0 ; 12 e- 2, 8, 2 13 Al Aluminum 13 p+ ; 14 n0 ; 13 e- 2, 8, 3 14 Si Silicon 14 p+ ; 14 n0 ; 14 e- 2, 8, 4 15 P Phosphorus 15 p+ ; 16 n0 ; 15 e- 2, 8, 5 16 S Sulfur 16 p+ ; 16 n0 ; 16 e- 2, 8, 6 17 Cl Chlorine 17 p+ ; 19 n0 ; 17 e- 2, 8, 7 18 Ar Argon 18 p+ ; 22 n0 ; 18 e- 2, 8, 8 19 K Potassium 19 p+ ; 20 n0 ; 19 e- 2, 8, 8, 1 20 Ca Calcium 20 p+ ; 20 n0 ; 20 e- 2, 8, 8, 2 Key: p+ - proton n0 - neutron e- - electron The nucleus of every atom contains two types of particle - protons and neutrons. ...read more.


Strong forces of attraction called chemical bonds hold atoms together in these compounds. Some compounds are very simple. For example, table salt contains just two elements, sodium and chlorine, bonded together. Its chemical name is sodium chloride. Other compounds are extremely complex, particularly substances found in living things, such as DNA and proteins. Ionic bonding Ionic bonding involves electron transfer between metals and non-metals. Both metals and non-metals try to achieve complete outer electron shell. Metals lose electrons from their outer shell and form positive ions (cations). This is an example of oxidation. Non-metals gain electrons into their outer shells and form negative ions. This is an example of reduction. The strong electrostatic attraction between ions of opposite charge is an ionic bond. An ionic compound is composed of a giant regular structure of ions. This regular structure makes ionic compounds crystalline. The strong forces of attractions between ions make it difficult to separate the ions, and ionic compounds therefore have high melting and boiling points. The ion formed by an element can be worked out from the position of the element in the periodic table. The elements in group 4 and group 8 (or 0) generally do not form ions. The formula of an ionic compound: Ionic compounds consist of positive and negative ions. A sample of the compound is uncharged because the positive and negative charges balance exactly. In a sample of calcium chloride, CaCl2, the number of chloride ions, Cl-, is exactly twice the number of calcium ions, Ca2+2Cl- or CaCl2. Covalent bonding Covalent bonding involves electron sharing. It occurs between atoms of non-metals. It results in the formation of a molecule. The non-metal atoms try to achieve complete outer electron shells. A single covalent bond is formed when two atoms each contribute one electron to a shared pair of electrons. For example, hydrogen gas exists as an H2 molecule. Each hydrogen atoms wants to fill its electron shell. ...read more.


50g of H2O (water) Thermometer Polystyrene cup Beaker Measuring cylinder Laboratory balance Method: I measured 50.0 cm3 (= 50g) of H2O and poured into the polystyrene cup. I noted the temperature which was 23oC. Then I measured 3g of NH4Cl. Next, I added it into the polystyrene cup which was containing the water. Then, I recorded the final temperature which was 18oC. Results: Volume of H2O 50.0 cm3 Weight of NH4Cl 3g Initial temperature of H2O 23oC Final temperature on mixing 18oC The c-value of the mixture can be taken as 4.2 Jg-1k-1 Theory 2: If the specific heat capacity of the solution is c and its mass is m then the heat required to release its temperature by ?T is: Q (J) = m x c x (?T) Calculations 1: 50.0 cm3 of H2O - initial temperature = 23oC final temp of the compound=18oC 3g of NH4Cl - solid Initial temperature = 23oC Final temperature= 18oC Rise in temp, ?T = 23 - 18 = 5oC Mass= 50.0 g + 3.0 g= 53 g, because 1 cm3 = 1g Heat (Q) = m x c x (?T) = 53 x 4.2 x 5 = 1113J = 1.113 kJ It means that 1.113 kJ is involved when 50 cm3 of H2O mixed with 3g of NH4Cl. Calculations 2: NH4Cl - 1 mole Relative atomic mass of NH4Cl: N=14; H=1; Cl=35.5 N+4xH+Cl 14+ (4x1) +35.5 = 53.5 53.5g = 1 mole 3g =3/53.5 mole �0.056 mole 3b The heat change is called the enthalpy change is denoted by delta H, ?H. o ?H is negative (-ve) for exothermic reactions i.e. heat energy is given out and lost from the system to the surroundings which warm up. o ?H is positive (+ve) for endothermic reactions i.e. heat energy is gained by the system and taken in from the surroundings which cool down OR, as is more likely, the system is heated to provide the energy needed to effect the change. ?? ?? ?? ?? 1 ...read more.

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