Free Acids, Bases and Salts MCQs with Answers

271. In this reaction, NH4+ + H2O -> H3O+ + NH3 the conjugate base of H3O+ ion is:

• A. NH4+
• B. H2O
• C. H+
• D. NH3

Explanation: A conjugate acid, within the Brønsted-Lowry acid-base theory, is a chemical compound formed when an acid donates a proton to a base-in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a hydrogen ion. Hence, Option B (H2O) is correct while other options are rendered as incorrect.

272. When NH3 gas is exposed to HCl, white fumes are formed which are chemically:

• A. NH4+
• B. NH4Cl
• C. HCl fumes
• D. Cl

Explanation: b) NH4Cl:NH4Cl is the correct chemical formula for ammonium chloride. When NH3 gas reacts with HCl gas, it forms ammonium chloride (NH4Cl), which is a white solid. The white fumes observed in this reaction are attributed to the formation of NH4Cl.

273. Water is amphoteric because:

• A. It acts both as an acid and a base
• B. It can dissolve both acids and bases
• C. It can give off H+ and OH- ions
• D. In its pure form, it has pH=7
• E. Both A and C

Explanation: Explanation for this question will be added soon.

274. Aqua Regia has 3 parts of _ and 1 part of _.

• A. HCL:H2SO4
• B. HCL:HNO3
• C. HNO3:H2SO4
• D. HNO3:HCL

Explanation: The explanation for this question will be added soon.

275. The multidentate ions are also called _agents.

• A. Oxidizing
• B. Reducing
• C. Chelating
• D. Chemical

Explanation: The explanation for this question will be added soon.

276. Strong Electrolytes are those which ionizes:

• A. Slowly
• B. Do not ionize
• C. Ionize rapidly
• D. None of these

Explanation: An electrolyte is a medium containing ions that is electrically conducting through the movement of ions so the strong electrolytes are those that ionize rapidly this means convert an atom, molecule, or substance into an ion or ions, typically by removing one or more electrons at more frequent rates.

277. The species which donates electrons to the central metal atom in the coordination sphere is called?

• A. Anion
• B. Cation
• C. The ligand is positively charged
• D. Acid

Explanation: Ligands are ions or neutral molecules that bond to a central metal atom or ion. Ligands act as Lewis bases (electron pair donors), and the central atom acts as a Lewis acid (electron pair acceptor).

278. Which one of the following is an electrophile?

• A. Br-
• B. CH4
• C. NH3
• D. H2O

Explanation: An electrophile is a species that lack electrons or has a positive charge on it. Br- is a nucleophile, along with H2O and NH3. CH4 is neither a nucleophile nor an electrophile. However, its radical, -CH+3 has electrophilic properties. So, out of all options, B option is the most suitable one.

279. If 9.8 g of sulfuric acid is dissolved in an excess quantity of water, it will yield _ moles of hydrogen ion ( H+) and _ mole of sulphate ions (SO4 -2).

• A. 0.1, 0.2
• B. 0.1, 0.3
• C. 0.2, 0.4
• D. 0.2, 0.1

Explanation: 9.8 grams of sulphuric acid is 0.1 moles so there will be 0.2 moles of hydrogen ions ( two hydrogens per sulphuric acid molecule) H2SO4 dissociates in 2 steps H2SO4 → H+ + HSO4- Therefore 0.1 mol H2SO4 will produce 0.1 mol H+ HSO4- ↔ H+ + SO4- Ka for this reaction is : 1.2 x 10-2 Calculate [H+] using Ka equation Ka = [H+]² / [HSO4- ] 1.2*10^-2 = [H+]² / 0.1 [H+]² = 0.1( 1.2*10^-2) [H+]² = 1.2*10^-3 [H+] = 0.035 M Total moles of H+ ions = 0.1 + 0.035 = 0.135 moles

280. NaHSO4 is a _ salt

• A. Normal
• B. Acidic
• C. Basic
• D. Amphoteric

Explanation: The explanation for this question will be added soon.