Testing Gases Evolved from Salts
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Questions and Answers

What gas is evolved when a colourless, odourless gas is produced with brisk effervescence which turns lime water milky?

  • H2S
  • NO2
  • SO2
  • CO (correct)
  • Which gas is indicated by the evolution of a colourless gas with the smell of rotten eggs that turns lead acetate paper black?

  • SO2
  • CH3COOH
  • CO
  • H2S (correct)
  • What gas is identified by its pungent smell, similar to burning sulphur, which turns acidified potassium dichromate solution green?

  • H2S
  • CO
  • NO2
  • SO2 (correct)
  • When brown fumes that turn acidified potassium iodide solution containing starch solution blue are observed, what gas is being tested?

    <p>NO2</p> Signup and view all the answers

    What gas is present if colourless vapours with a vinegar-like smell are noted, which turn blue litmus red?

    <p>CH3COOH</p> Signup and view all the answers

    Which gas is revealed when testing confirms the presence of a carbonate anion?

    <p>H2S</p> Signup and view all the answers

    What is the purpose of dipping the clean loop of the platinum wire in a paste of salt and concentrated hydrochloric acid?

    <p>To identify the metal ion through the flame test</p> Signup and view all the answers

    Why is the borax bead test employed only for coloured salts?

    <p>Because borax forms colored beads with metal salts</p> Signup and view all the answers

    What does a colored borax bead indicate during the borax bead test?

    <p>Impurity in the salt sample</p> Signup and view all the answers

    Why is it crucial to confirm that the borax bead formed is transparent and colorless before performing the test?

    <p>To prevent contamination from other substances</p> Signup and view all the answers

    What does observing the flame color through a blue glass help achieve during the flame test?

    <p>Identifying metal ions more accurately</p> Signup and view all the answers

    What does a green flame with a blue center signify during the flame test?

    <p>$Cu^{2+}$ ion presence</p> Signup and view all the answers

    What is the product of the reaction between 2NaNO2 and H2SO4?

    <p>Na2SO4 + 2HNO2</p> Signup and view all the answers

    In the Griss-Ilosvay test, what color dye is formed when sulphanilic acid is diazotised and couples with 1-naphthylamine?

    <p>Red dye</p> Signup and view all the answers

    What does a fruity odor of ethyl acetate indicate in the presence of acetate ions?

    <p>Presence of CH3COO ions</p> Signup and view all the answers

    What is the color change observed when acetate ions react with neutral ferric chloride solution?

    <p>Red color</p> Signup and view all the answers

    What happens when I2 reacts with starch?

    <p>Blue complex</p> Signup and view all the answers

    What are the products formed when 2HNO2, 2KI, and 2CH3COOH react together?

    <p>2CH3COOK + 2H2O + 2NO + I2</p> Signup and view all the answers

    What gas is evolved when 0.1 g of salt is mixed with manganese dioxide and conc.sulphuric acid?

    <p>Chlorine gas</p> Signup and view all the answers

    Which anion is confirmed by the formation of a curdy white precipitate upon adding silver nitrate to the sodium carbonate extract?

    <p>Iodide (I)</p> Signup and view all the answers

    What color does the solution turn when the gas evolved from the reaction mixture is passed through sodium hydroxide solution?

    <p>Yellow</p> Signup and view all the answers

    Which reagent is used to acidify one part of the divided solution to confirm the presence of a specific anion?

    <p>Acetic acid</p> Signup and view all the answers

    What is indicated by the evolution of intense brown fumes in the last step of the experiment?

    <p>Decomposition of MnO2</p> Signup and view all the answers

    What is the role of borax in flame tests for metal ions?

    <p>To form metaborate of the metal being tested</p> Signup and view all the answers

    What reaction occurs in the reducing flame involving cupric metaborate?

    <p>$2Cu(BO_2)_2 + 4NaBO_2 + 2C → 2Cu + 2Na_2B_4O_7 + 2CO$</p> Signup and view all the answers

    Why is it important to observe the color of the bead both when hot and when cold?

    <p>The cooling process affects the color intensity</p> Signup and view all the answers

    What information can be obtained from the preliminary identification of metal ions using Table 7.9?

    <p>The specific metal present in the sample</p> Signup and view all the answers

    What is the purpose of tapping the platinum wire with your finger to remove the bead?

    <p>To release the bead without damaging the wire</p> Signup and view all the answers

    Why does borax lose its water of crystallisation during heating?

    <p>To decompose into various compounds for flame tests</p> Signup and view all the answers

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