MFL. OCR Decision Mathematics 1 (4736) Revision - Waldomaths. French. Home | Doddle. Homepage. Grammar. Jws6th.
Pearltrees tips. Chemistry. Empirical and Molecular Formula Calculations. Custom Search Back to Percent Composition by Mass Empirical formula is the smallest whole number ratio of moles of each element in a compound. CaCl2 --> there is 1 mole of calcium for every 2 moles of chlorine Level 1 Simple Empirical formula questions What is the empirical formula of the following compounds? Level 2 Empirical Formula Calculation Steps Step 1 If you have masses go onto step 2. If you have %. Step 2 Determine the moles of each element. Step 3 Determine the mole ratio by dividing each elements number of moles by the smallest value from step 2. Step 4 Double, triple … to get an integer if they are not all whole numbers Molecular Formula (additional steps) The question should have included a molecular mass.
Step 5 Determine the mass of your empirical formula Step 6 Divide the given molecular mass by your E.F. mass in step 5 Step 7 Multiply the atoms in the empirical formula by this number (Hint-Save the molar mass 194.19g/mol until the end) 49.48% C, 5.190%H, 16.47% O and 28.85% N ***note. Chemguide: helping you to understand Chemistry - Main Menu. Shapes of Molecules. Shapes of molecules and ions containing single bonds. Methane and the ammonium ion are said to be isoelectronic. Two species (atoms, molecules or ions) are isoelectronic if they have exactly the same number and arrangement of electrons (including the distinction between bonding pairs and lone pairs). The hydroxonium ion, H3O+ Oxygen is in group 6 - so has 6 outer electrons. Add 1 for each hydrogen, giving 9. Take one off for the +1 ion, leaving 8. This gives 4 pairs, 3 of which are bond pairs. Five electron pairs around the central atom A simple example: phosphorus(V) fluoride, PF5 (The argument for phosphorus(V) chloride, PCl5, would be identical.)
Phosphorus (in group 5) contributes 5 electrons, and the five fluorines 5 more, giving 10 electrons in 5 pairs around the central atom. The 5 electron pairs take up a shape described as a trigonal bipyramid - three of the fluorines are in a plane at 120° to each other; the other two are at right angles to this plane. A tricky example, ClF3 Chlorine is in group 7 and so has 7 outer electrons. Science aid: Electron Arrangement.
Electron Arrangement Electron Arrangement This topic often confuses people so don't worry if you don't understand it first time. Read up on electron arrangment in textbooks and get other people to explain it to you. Before this level of study you will have been told that electrons have fields of 2,8,8 maximum capacity. Well, this is not true. As well as main energy levels, there are also sub-shells. For these sub-shells it is important to note that the 4s requires less energy for electrons to enter it than the 3d. On the image, highlighted in blue are two features: The first is that at Scantium (Sc) the electrons in 3d start to fill up after 4s.The second is [Ne], this is a shorthand way of writing the electronic configuration, the bit highlighted means the electron configuration of Neon then the rest.
The pattern of first ionisation energies across a period is a little more complex, because it does not show a perfect pattern. The mass spectrometer - how it works. Assuming 1+ ions, stream A has the lightest ions, stream B the next lightest and stream C the heaviest. Lighter ions are going to be more deflected than heavy ones. Detection Only ion stream B makes it right through the machine to the ion detector. The other ions collide with the walls where they will pick up electrons and be neutralised. Eventually, they get removed from the mass spectrometer by the vacuum pump. When an ion hits the metal box, its charge is neutralised by an electron jumping from the metal on to the ion (right hand diagram). A flow of electrons in the wire is detected as an electric current which can be amplified and recorded. Detecting the other ions How might the other ions be detected - those in streams A and C which have been lost in the machine?
Remember that stream A was most deflected - it has the smallest value of m/z (the lightest ions if the charge is 1+). Enthalpy - ChemWiki. Enthalpy Change Accompanying a Change in State of Matter When a liquid vaporizes the liquid must absorb heat from its surroundings to replace the energy taken by the vaporizing molecules in order for the temperature to remain constant. This heat required to vaporize the liquid is called enthalpy of vaporization, or often, heat of vaporization. For example, the vaporization of one mole of water the enthalpy is given as: ΔH = 44.0 kJ at 298 K When a solid melts, the required energy is similarly called enthalpy of fusion, or heat of fusion.
ΔH = 6.01 kJ at 273.15 K Enthalpy can also be expressed as a molar enthalpy, , by dividing the enthalpy or change in enthalpy by the number of moles. If there is no non-expansion work on the system and the pressure is still constant, then the change in enthalpy will equal the heat consumed or released by the system (q). This relationship can help to determine whether a reaction is endothermic or exothermic. Chemistry. Science and Engineering. Latin. CSCP - Cambridge Latin Course - Home. Roman Gladiator Types. Different gladiators specialized in different weapons and tactics.
The following illustrates these various styles and equipment. Of these,Thracians, Mirmillones, Retiarii, and Secutores were four of the most common. Andabatae: (1st cent. BC) Clad in chainmail like eastern cavalry (cataphracti), wore visored helmets without eye holes. They charged blindly at one another on horseback as an ancient precursor to the medieval joust. Bestiarii: (beast fighters) originally armed with a spear or knife, these gladiators were condemned to fight beasts with a high probability of death.
Dimachaeri: Used two-swords, one in each hand. Equites: Fought on horseback with a spear and gladius, dressed in a full tunic, with a manica (arm-guard). Essedari: Celtic style charioteers, likely first brought to Rome from Britain by Caesar. Hoplomachi (heavily armed) or Samnite: Fully armored, and based on Greek hoplites. Laquerii: Laqueatores used a rope and noose. Samnites: see Hoplomachi. Category. As of July 1, 2013 ThinkQuest has been discontinued. We would like to thank everyone for being a part of the ThinkQuest global community: Students - For your limitless creativity and innovation, which inspires us all. Teachers - For your passion in guiding students on their quest.
Partners - For your unwavering support and evangelism. Parents - For supporting the use of technology not only as an instrument of learning, but as a means of creating knowledge. We encourage everyone to continue to “Think, Create and Collaborate,” unleashing the power of technology to teach, share, and inspire. Best wishes, The Oracle Education Foundation. Biology. BiologyMad A-Level Biology. ISA Practical Investigations - Glossary. BIOG 1105-1106 | Cornell Introductory Biology, Individualized Instruction. Mathematics. A-level Maths Revision, GCSE Maths, SAT and IB Math Revision Videos from ExamSolutions.