29 Questions
What gas is evolved when a colourless, odourless gas is produced with brisk effervescence which turns lime water milky?
CO
Which gas is indicated by the evolution of a colourless gas with the smell of rotten eggs that turns lead acetate paper black?
H2S
What gas is identified by its pungent smell, similar to burning sulphur, which turns acidified potassium dichromate solution green?
SO2
When brown fumes that turn acidified potassium iodide solution containing starch solution blue are observed, what gas is being tested?
NO2
What gas is present if colourless vapours with a vinegar-like smell are noted, which turn blue litmus red?
CH3COOH
Which gas is revealed when testing confirms the presence of a carbonate anion?
H2S
What is the purpose of dipping the clean loop of the platinum wire in a paste of salt and concentrated hydrochloric acid?
To identify the metal ion through the flame test
Why is the borax bead test employed only for coloured salts?
Because borax forms colored beads with metal salts
What does a colored borax bead indicate during the borax bead test?
Impurity in the salt sample
Why is it crucial to confirm that the borax bead formed is transparent and colorless before performing the test?
To prevent contamination from other substances
What does observing the flame color through a blue glass help achieve during the flame test?
Identifying metal ions more accurately
What does a green flame with a blue center signify during the flame test?
$Cu^{2+}$ ion presence
What is the product of the reaction between 2NaNO2 and H2SO4?
Na2SO4 + 2HNO2
In the Griss-Ilosvay test, what color dye is formed when sulphanilic acid is diazotised and couples with 1-naphthylamine?
Red dye
What does a fruity odor of ethyl acetate indicate in the presence of acetate ions?
Presence of CH3COO ions
What is the color change observed when acetate ions react with neutral ferric chloride solution?
Red color
What happens when I2 reacts with starch?
Blue complex
What are the products formed when 2HNO2, 2KI, and 2CH3COOH react together?
2CH3COOK + 2H2O + 2NO + I2
What gas is evolved when 0.1 g of salt is mixed with manganese dioxide and conc.sulphuric acid?
Chlorine gas
Which anion is confirmed by the formation of a curdy white precipitate upon adding silver nitrate to the sodium carbonate extract?
Iodide (I)
What color does the solution turn when the gas evolved from the reaction mixture is passed through sodium hydroxide solution?
Yellow
Which reagent is used to acidify one part of the divided solution to confirm the presence of a specific anion?
Acetic acid
What is indicated by the evolution of intense brown fumes in the last step of the experiment?
Decomposition of MnO2
What is the role of borax in flame tests for metal ions?
To form metaborate of the metal being tested
What reaction occurs in the reducing flame involving cupric metaborate?
$2Cu(BO_2)_2 + 4NaBO_2 + 2C → 2Cu + 2Na_2B_4O_7 + 2CO$
Why is it important to observe the color of the bead both when hot and when cold?
The cooling process affects the color intensity
What information can be obtained from the preliminary identification of metal ions using Table 7.9?
The specific metal present in the sample
What is the purpose of tapping the platinum wire with your finger to remove the bead?
To release the bead without damaging the wire
Why does borax lose its water of crystallisation during heating?
To decompose into various compounds for flame tests
Learn how to perform a test to identify gases evolved from salts by adding dilute sulphuric acid and observing the reaction. Use the provided apparatus to confirm the identity of the gas evolved. Refer to Table 7.1 for characteristic properties of gases.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
