NSS Chemistry Part 15 Analytical Chemistry (Structural Questions) HKCEE and HKAL Past Paper Questions 1. HKCEE 1994 Q8b A student carried out some tests on an ionic compound X which was a white solid. The results obtained were summarized in the following flow diagram: (i) Based on the above information‚ deduce the cation and anion present in X. (ii) Describe how the flame test on X can be carried out in the laboratory. (6 marks) 1 2. HKCEE 1995 Q2 In each of the following
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Qualitative Analysis of Cations Short Overview The most common cations have been placed into five groups based upon solubility in aqueous solutions when different reagents are added. The reactions which occur are useful in identifying the presence of these cations in unknown samples. The process of identifying the cations is called qualitative analysis. The purpose of this experiment is to identify which cations are present in unknown solutions. A data sheet was not prepared for this experiment
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4.02 chemistry notes Law of Conservation of Mass One of the most important principles of chemistry is the law of conservation of mass. This law states that matter is neither created nor destroyed during an ordinary chemical reaction. In other words‚ all of the atoms that were present at the beginning of a reaction are present at the end of the reaction—they have just been rearranged to bond differently and form new substances. It is important that chemical equations represent this law by always
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very low solubility in water. NH4Cl has a very high solubility in water. Thus‚ the mixture could be put in water and decanted. This would separate the two substances. 3. BaCl2 is very soluble in water but CaSO4 is not. So add water. Then filtrated to get the BaSO4. Evaporate the solution and you get back BaCl2. 4. Just add water. The potassium bromide will go into solution‚ the naphthalene will not. Filter off the naphthalene. Allow the water in the potassium solution to evaporate
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Once it has been dissolved from the other two cations‚ it is centrifuged and the liquid is decanted into another test tube. Once in the other test tube‚ a drop of 6.0 M acetic acid and two drops of 1.0 M K2CrO4 is added to the saved liquid. If the lead (II) cation is present‚ a yellow precipitate forms and ensures the presence of that cation. When testing my unknown solution‚ the lead (II) ion was not present in my solution. To further separate the cations
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1 mole of any substance can be defined as: Amount of a substance that contains as many particles (atoms‚ molecules or ions) as there are atoms in 12 g of the 12C isotope Avogadro number or Avogadro constant (NA); equal to 6.022 × 1023 particles Example − 1 mole of oxygen atoms = 6.022 × 1023 atoms 1 mole of carbon dioxide molecules = 6.022 × 1023 molecules 1 mole of sodium chloride = 6.022 × 1023 formula units of sodium chloride Molar mass of a substance can be defined as: Mass of one mole
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Chem 102 - Lab #2 Quantitative Analysis of a Soluble Sulfate Steven English Lab Instructor: Dr. Campo Date: Tuesday‚ February 5th 2013 Pre-Lab Questions A. Adding the acid to the sodium sulfate solution results in an increase in the solubility of any free anions present in the sample. This will happen because the present anions will bind with the hydrogen cations present in the acid. B. The sodium sulfate is boiled because experiments have shown that barium sulfate is 50
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is soluble or insoluble in water. a. MgBr2 d. Sr(OH)2 b. PbI2 e. ZnSO4 c. (NH4)2CO3 5. (Brown 4.20 w/ additional) Predict whether each of the following compounds is soluble in water: a. AgI f. Sr(NO3)2 b. Na2CO3 g. CuSO4 c. BaCl2 h. CuCl2 d. Al(OH)3 g. PbS e. Zn(CH3COO)2 6. Complete the following double replacement (exchange ) reactions. Be sure to balance them. a. MgCl2 + Ba(NO3)2 → b. Al2(CrO4)3 + (NH4)2SO4 → c. K2SO4 + SrCl2 → d. FeCl3 + KOH →
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number of sulphur in each of the following cases? a) S2b) H2SO4 c) S2O32d) CS2 e) S8 7. To prepare 100 g of 19.7% by weight solution of NaOH‚ how many grams each of NaOH and H2O are needed? 8. Balance the following equations: a) Fe2(SO4)3 + BaCl2 b) Ba(OH)2 + HCl c) BaSO4 + CuCl2 d) Zn + H2SO4 9. Balance the following skeleton reactions and identify the oxidizing and reducing agents (ion-electron method). MnO4 (aq) + H2O2(aq) Mn2+(aq) + O2(g)
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Finding the Ratio of Moles of Reactants in a Chemical Reaction Purpose: The goal of the lab is to determine the mole ratio of two reactants in a chemical reaction (AgNO3 and K2CrO4). However‚ the formulas for the products are unknown. Introduction: When determining the molar ratio of a chemical equation‚ usually the formulas of the reactants and the products are known. With that information‚ it is particularly easy to determine the ratio. However‚ since the products and the formulas for
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