Analytical Chemistry Quiz - ICSE Class 10 Chemistry

Free practice quiz: Analytical Chemistry (ICSE Class 10 Chemistry). 52 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. A sample of an unknown substance is subjected to flame test. It produces a brick-red flame. Which of the following cations is most likely present in the sample?

   1. Lithium (Li+)
   2. Sodium (Na+)
   3. Potassium (K+)
   4. Calcium (Ca2+)
   Show answer

   Answer: D. Calcium (Ca2+)

   The flame test is a qualitative analysis technique used to identify the presence of certain metal ions. Different metal ions produce characteristic flame colors. Lithium ions produce a red flame, sodium ions produce a yellow-orange flame, potassium ions produce a lilac flame, and calcium ions produce a brick-red flame.

2. In a Karl Fischer titration, which is used to determine the amount of water in a sample, the key reagent is the Karl Fischer reagent. This reagent typically contains sulfur dioxide (SO2), iodine (I2), a base, and an alcohol (like methanol). The reaction involves the reduction of iodine by water in the presence of SO2 and the base. A sample with a higher water content will require:

   1. More Karl Fischer reagent to reach the endpoint
   2. Less Karl Fischer reagent to reach the endpoint
   3. The same amount of Karl Fischer reagent regardless of water content
   4. No Karl Fischer reagent
   Show answer

   Answer: A. More Karl Fischer reagent to reach the endpoint

   The Karl Fischer titration is based on a quantitative reaction between water and the Karl Fischer reagent. The amount of reagent consumed is directly proportional to the amount of water present in the sample. Therefore, a sample with a higher water content will consume more Karl Fischer reagent to reach the endpoint, where an excess of iodine is detected (usually visually or electrochemically).

3. In a flame photometry analysis, the intensity of the emitted light is directly proportional to the concentration of the analyte in the sample. If a calibration curve is constructed by plotting emission intensity versus concentration, a linear relationship is observed within a certain concentration range. This linear relationship is an application of which principle?

   1. Le Chatelier's Principle
   2. Beer-Lambert Law
   3. Hess's Law
   4. Arrhenius Equation
   Show answer

   Answer: B. Beer-Lambert Law

   While flame photometry is an emission technique and Beer-Lambert law is primarily for absorption, the underlying principle of proportionality between the measured signal (emission intensity in this case) and the concentration of the analyte is analogous to the Beer-Lambert Law (A = εbc), where absorbance is directly proportional to concentration and path length. In emission spectroscopy, the intensity of emitted light is proportional to the number of excited atoms, which in turn is proportional to the concentration of the element in the sample.

4. A sample is tested with Nessler's reagent (an alkaline solution of potassium mercuric iodide). A yellow to brown precipitate or coloration is observed. This is a characteristic test for the presence of:

   1. Sulfite ions
   2. Ammonia and ammonium ions
   3. Chloride ions
   4. Sulfate ions
   Show answer

   Answer: B. Ammonia and ammonium ions

   Nessler's reagent is a specific reagent used for the detection of ammonia and ammonium ions. In alkaline solution, Nessler's reagent reacts with ammonia (NH3) or ammonium ions (which form NH3 in alkaline conditions) to produce a yellow to brown precipitate or color, which is believed to be an iodinated addition compound of mercury and ammonia (e.g., HgO·Hg(NH2)I).

5. When testing for the presence of phosphate ions, a solution containing ammonium molybdate and nitric acid is used. The formation of a yellow precipitate indicates the presence of phosphate. What is the chemical formula of this characteristic yellow precipitate?

   1. H3PO4
   2. MgNH4PO4·6H2O
   3. (NH4)3PO4·12MoO3
   4. Pb3(PO4)2
   Show answer

   Answer: C. (NH4)3PO4·12MoO3

   The yellow precipitate formed when testing for phosphate ions with ammonium molybdate in nitric acid is ammonium phosphomolybdate, with the general formula (NH4)3PO4·12MoO3 (or variations thereof depending on conditions). Magnesium ammonium phosphate hexahydrate (MgNH4PO4·6H2O) is a precipitate formed in the presence of magnesium ions and ammonium ions, used as a confirmatory test for phosphate in some schemes, but the primary test with ammonium molybdate yields ammonium phosphomolybdate.

More quizzes

• Chemical Bonding
• Electrolysis
• Metallurgy
• Mole Concept & Stoichiometry
• Mole Concept and Stoichiometry
• Organic Chemistry

Browse all Chemistry quizzes