Chapter 2 22. A student heats 0.5585 g of iron with 0.3550 g of sulfur. She reports that she obtains 0.8792 g of iron sulfide and recovers 0.0433 g of unreacted sulfur. Show by calculation whether or not her results obey the law of conservation of mass. Total mass initial = 0.5585 g + 0.3550 g = 0.9135 g Total mass final = 0.8792 g + 0.0433 g = 0.9225 g These two values should be equal by the law of conservation of mass. These results do not obey the law of conservation of mass. Possibly she
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SALTS AND THEIR PREPARATION SALTS A salt is a compound formed when the hydrogen ions in an acid are replaced by metal ions or by ammonium ions. Compounds in which the H+ ions in an acid have been replaced by ammonium ions (NH4+) are called ammonium salts. NOTE: •An anion is a negatively charged ion. Hence:•Hydrochloric acid gives chlorides. E.g. sodium chloride‚ ammonium chloride. •Nitric acid gives nitrates. E.g. barium nitrate‚ copper nitrate. •Sulphuric acid gives sulphates. E.g. silver sulphate
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happens because as the metal gets warmer‚ the metal ions in the wire gain kinetic energy and start to vibrate. As their motion becomes more erratic they are more likely to get in the way and disrupt the flow of the electrons and therefore increase the resistance. Length of the wire This is easier to explain using the "hallway" analogy. Imagine in a corridor‚ there are some people (electrons) trying to move‚ and there are some people (ions) staying still. If the corridor was very short‚ there
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The plasma and Bose-Einstein Condensate states of matter‚ while having some similarities‚ are two completely different forms of matter and connect with the Kinetic Molecular Theory in differing ways. Plasma is the fourth state of matter. It’s a fluid‚ gas-like substance that consists of a mixture of free electrons‚ neutral atoms‚ and charged ions. It is made up of both positively and negatively charged particles‚ which contributes to plasma’s ability to react to and create electromagnetic forces.
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away/donate/release its (outermost) electron more | | | | | |easily/readily. | |1 | | | |or‚ Rb can form ion/cation/positive ion more easily/readily. | |(1) | | | |or‚ The strength of metallic bond between Rb atoms is weaker than that between K atoms/Rb can atomize more | | | |
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Student Number Mark / 39 Chemistry Preliminary Course Final Examination • 2006 General Instructions • • • • • • • Reading time – 5 minutes Working time – 45 minutes Write using black or blue pen Draw diagrams using pencil Board-approved calculators may be used A Data Sheet and a Periodic Table are provided Write your Student Number at the top of this page Total Marks – 39 Part A – 10 marks • Attempt Questions 1 – 10 • Allow about 10 minutes for this part Part B – 29 marks • Attempt
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Chapter 1 Chemical Reactions and Equations Q.1. Why should magnesium ribbon be cleaned before burning in air ? Ans: Magnesium ribbon is a very reactive metal. When stored it reacts with oxygen to form a layer of magnesium oxide on its surface. This layer of magnesium oxide being a stable compound prevents further reaction of magnesium with oxygen. The magnesium is cleaned before burning in air to remove this layer so that the metal can be exposed to air properly. Q.2. Write the balanced
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Title of Experiment: An Activity Series Lab MSDS: Copper‚ Cu(s) Stability- Stable. Incompatible with strong acids‚ active halogen compounds‚ chlorine‚ fluorine‚ iodine‚ bromine‚ ammonia. May react explosively with strong oxidizing agents. Toxicology-Dust may cause respiratory irritation. Personal Protection- Suitable ventilation if handling powder. Zinc‚ Zn(s) Stability-Stable. Incompatible with amines‚ cadmium‚ sulfur‚ chlorinated solvents‚ strong acids‚ strong bases. Air and moisture
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1 : 2 C. 2 : 1 D. 1 : 3 E. 3 : 1 24. A solution contains the ions Ag+‚ Pb2+‚ and Ni2+. Dilute solutions of NaCl‚ Na2SO4‚ and Na2S are available to separate the positive ions from each other. In order to effect separation‚ the solutions should be added in which order? A. Na2SO4‚ NaCl‚ Na2S B. Na2SO4‚ Na2S‚ NaCl C. Na2S‚ NaCl‚ Na2SO4
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ratios (solute to solution) x a million (106). In this sense‚ they are similar to wt %‚ which could be thought of as parts per hundred (although nobody uses this term). Other variations on this theme include: ppt – parts per thousand (used for common ions in sea water) ppb – parts per billion (used for heavy metals and organics) ppt – parts per trillion (used for trace metals and trace organics) The following table summarizes common mass ratios for solutions and solids. Unit Solutions Solids ppm mg/L
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