Basic Concepts of Chemistry MCQ Quiz - Objective Question with Answer for Basic Concepts of Chemistry - Download Free PDF

The correct answer is H.

Key Points

• H is present in all atoms except neutrons.
  • The available hydrogen state H¹.
  • It is made of 1 electron, 1 proton, and no neutrons.
  • All other elements including isotopes of Hydrogen have neutrons.
  • Neutrons are present in the nucleus of all atoms, except hydrogen.
• All elements have atoms with neutrons except for one.
  • The normal hydrogen (H) atom does not have any neutrons in its tiny nucleus.
  • That tiny little atom (the tiniest of all) has only one electron and one proton.
  • Deuterium is a hydrogen atom with an extra neutron and tritium has two extra.

Additional Information

• Avogadro’s number is an absolute number: there are 6.023×1023 elementary entities in 1 mole.
  • This can also be written as 6.023×1023 mol-1.
• The mass of one mole of a substance is equal to that substance’s molecular weight.
  • For example, the mean molecular weight of water is 18.015 atomic mass units (amu), so one mole of water weighs 18.015 grams.
• Mole:
  • The amount of substance of a system that contains as many elementary entities as there are atoms in 12 g of carbon-12. 
  • The mole allows scientists to calculate the number of elementary entities (usually atoms or molecules ) in a certain mass of a given substance.

The correct answer is Copper and Tin.

• An alloy is a homogenous mixture of metal with another metal or non-metal.
• Bronze is an alloy of copper and tin.
  • It consists of around 88% copper and 12% tin.
  • Bronze is typically used for bearings.
• Brass is an alloy of copper and zinc.
• Constantan is an alloy of copper and nickel.
• Aluminum bronze is an alloy of copper and aluminum.

The correct answer is Ethanol

• Ethanol is an active ingredient in all alcoholic drinks.

Key Points

• Ethanol is a member of a class of organic compounds that are given the general name alcohol. 
• Its molecular formula is C2H5OH. 
• It is also called ethyl alcohol.
• Ethanol is also the intoxicating ingredient of many alcoholic beverages such as beer, wine, and distilled spirits.
• As an industrial chemical it is used as a solvent, in the synthesis of other organic chemicals, and as an additive for automotive gasoline.

Additional Information

• Pentane is an organic compound that is a clear colorless liquid. It is an alkane with five carbon atoms. 
• Butane is an alkane with the formula C₄H₁₀. It is a colorless gas with a faint petroleum-like odor.
• Propane is a flammable hydrocarbon gas. It is commonly used for fuel in heating, cooking, hot water and vehicles.

CONCEPT:

Avogadro's Law and Molar Relationships at STP

• Avogadro's Law: At Standard Temperature and Pressure (STP), 1 mole of any ideal gas occupies 22.4 liters of volume.
• Molecular Relationships:
  • 1 mole of a substance contains Avogadro's number of molecules, which is 6.022 × 10²³.
  • 1 mole of a compound is equivalent to its molar mass in grams.

EXPLANATION:

• Half mole of nitrogen gas is measured 11.2 liters at STP.
  • At STP, 1 mole of nitrogen gas occupies 22.4 liters.
  • Thus, half a mole of nitrogen gas will occupy 22.4 ÷ 2 = 11.2 liters.
  • This statement is correct.
• 17 grams of ammonia gas contains 6.022 × 10²³ molecules at STP.
  • The molar mass of ammonia (NH₃) is 14 (N) + 1×3 (H) = 17 g/mol.
  • 17 grams of ammonia corresponds to 1 mole, which contains 6.022 × 10²³ molecules.
  • This statement is correct.
• 22.4 liters of CO₂ gas at STP contains 44 grams of molecules.
  • The molar mass of CO₂ is 12 (C) + 16×2 (O) = 44 g/mol.
  • At STP, 22.4 liters of CO₂ corresponds to 1 mole, which weighs 44 grams.
  • This statement is correct.
• 4 grams of hydrogen gas contains 6.022 × 10²³ molecules.
  • The molar mass of H₂ is 1×2 = 2 g/mol.
  • 4 grams of H₂ corresponds to 4 ÷ 2 = 2 moles.
  • Since 1 mole contains 6.022 × 10²³ molecules, 2 moles would contain 2 × 6.022 × 10²³ = 1.2044 × 10²⁴ molecules.

The given statement is incorrect because 4 grams of H₂ does not contain 6.022 × 10²³ molecules, but rather twice that amount.

Therefore, the incorrect statement is Option 4.

The correct answer is Amalgam.

Important Points

• Amalgam is a special class of alloys in which one metal is mercury.
  • Silver amalgam is the amalgam used for a dental filling.
  • Gold amalgam is the amalgam used in the extraction of gold from ore.
  • The metal mercury is kept inside an iron container because iron doesn't form an amalgam with mercury.
• Mercury is a chemical element with atomic number 80.
  • Mercury is also known as quicksilver.
  • Mercury is the metal that is liquid at room temperature.
  • Mercury is the first known superconductor.
  • Cinnabar is the ore of mercury.

Additional Information

• Brass is the alloy of copper and zinc.
• Nichrome is the alloy of nickel, chromium, and iron.
• Electrum is the alloy of gold and silver.

Key Points

• A deposition is a process by which a gas is converted into a solid.
• Sublimation is the process by which a solid is converted to gas directly without changing into liquid in between.
• Vaporisation is the process of conversion of a liquid into a gas (vapor).
• Freezing is a process of conversion of liquid into solid at the freezing point.

The correct answer is Amalgam.

Important Points

• Amalgam is a special class of alloys in which one metal is mercury.
  • Silver amalgam is the amalgam used for a dental filling.
  • Gold amalgam is the amalgam used in the extraction of gold from ore.
  • The metal mercury is kept inside an iron container because iron doesn't form an amalgam with mercury.
• Mercury is a chemical element with atomic number 80.
  • Mercury is also known as quicksilver.
  • Mercury is the metal that is liquid at room temperature.
  • Mercury is the first known superconductor.
  • Cinnabar is the ore of mercury.

Additional Information

• Brass is the alloy of copper and zinc.
• Nichrome is the alloy of nickel, chromium, and iron.
• Electrum is the alloy of gold and silver.

The correct answer is 18 g.

Key Points

Explanation:

• 0.1 mole of C₆H₁₂O₆ = Molecular mass of C6H12O6 in grams
  • 0.1 (Mass of 6C + Mass of 12H + Mass of 6O)
  • 0.1 (12 × 6 + 1 × 12 + 16 × 6)
  • 0.1 (72 + 12 + 96)
  • 18 grams

The correct answer is Ca(OH)₂.

Key Points

• When quick lime (CaO)reacts with water, lime water is produced.
• CaO +H₂O→Ca(OH)₂
• Here the product is Ca(OH)₂, which is slaked lime or lime water.
• Mainly Calcium carbonate disassociates to produce quick lime and carbon dioxide.
• Then the quick lime reacts with water and produces lime water.
• Calcium hydroxide is used in many applications, including food preparation.
• Limewater is the common name for a saturated solution of calcium hydroxide.

The correct answer is Potassium.

Key Points

• Potassium belongs to a group - (1) and period - (IV) of the periodic table. Hence among the given options, Potassium has a maximum atomic radius.
• Carbon and Nitrogen belong to the period - (II) of the periodic table and on the right side hence it is obvious that atomic radii of Carbon and Nitrogen are very much small than Sodium and Potassium.
• Sodium and Potassium belong to a group - (1) and  Potassium is placed below Sodium hence the atomic radius of Potassium more than Sodium.

Important Points 

• The atomic size generally decreases across a period as we move from left to right in a particular period. due to an increase in nuclear charge.
• The atomic size generally increases across groups as we move from top to bottom in a particular group due to the addition of new shells to atoms.

Additional Information

The correct answer is 20.

CONCEPT:

• Heavy water: It is a form of water that contains only deuterium rather than the common hydrogen-1 isotope that makes up most of the hydrogen in normal water.
  • Formula: D₂O
  • Boiling point:101.4 °C
  • Molar mass: 20 gm/mole
  • Melting point: 3.8 °C
  • Density: 1.11 gm/cm³
  • Refractive index:1.328

EXPLANATION:

• Heavy water has deuterium(D) which is an isotope of hydrogen.
• While hydrogen has 1 proton and 0 neutrons in its nucleus giving it an atomic weight of 1, deuterium has 1 proton and 1 neutron in its nucleus.
• So deuterium has atomic weight 2.
• So heavy water, which has molecular formula D₂O, has molecular mass = 16(for oxygen)+(2× 2)(for two deuteriums)= 20

The correct answer is Na.

• The decreasing order of atomic radius is Na (227pm) > P (195pm) > S (180pm) > Cl (175pm).

Explanation:

• When two atoms have the same value of n for the valence electrons, the atom with the greater number of protons will generally have a greater effective nuclear charge to draw the valence electrons closer to the nucleus and, thus, decrease the atomic radius. 
• Since chlorine's 17 protons are greater than sodium's 11 protons, chlorine will have a greater effective nuclear charge to draw chlorine's valence electrons closer to the nucleus and, thus, chlorine is expected to have a smaller atomic radius.
• While sodium with the lower effective nuclear charge is expected to have a larger atomic radius.

Important Points

• In the periodic table, the atomic radius of elements tends to decrease as you move across a row from left to right.
• Ionic radii increase down a group as more shells are added.

Key Points

• Sodium is highly reactive so that it is stored in oil or kerosene because it spontaneously ignites in water.
• At room temperature, sodium metal is soft enough that you can cut it with a butter knife.
• White phosphorus is used in flares and incendiary devices.
• Red phosphorus is in the material stuck on the side of matchboxes, used to strike against safety matches to light them.

The correct answer is Siderite.

• Naturally occurring mineral from which a metal can be extracted is called an ore.
• The impurities present in an ore is called gangue.
• Iron ores are the minerals from which metallic iron is extracted. 
• Among the options, only siderite is an ore of Iron.
  • The chemical formula of siderite is FeCO₃.
  • Siderite consist of 48.2% of iron.
• The other important ores of iron are:
  • Magnetite.
  • Hematite
  • Goethite.
  • Limonite.
• Malachite is an ore of Copper.
• Bauxite is an ore of Aluminium.
• Anglesite is a minor ore of lead.

The correct answer is John Dalton.

Key Points

• This law of multiple proportions is also known as Dalton's law because this law was announced (1803) by the English chemist John Dalton.
• Law of multiple proportions:
  • if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element, are in the ratio of small whole numbers.
  • Hydrogen combines with oxygen to form two compounds, water and hydrogen peroxide.
    Hydrogen + Oxygen → Water
          2g             16g          18g
    Hydrogen + Oxygen → Hydrogen Peroxide
          2g             32g          34g
  • Masses of oxygen is16 g (in water) and 32 g (in hydrogen peroxide) combine with 2g of hydrogen, bear a simple ratio, 16:32 or 1: 2.

Additional Information

• Avogadro's Law: Equal volumes of all gases at the same temperature and pressure should contain the equal number of molecules. 
• Gay Lussac's law of gaseous volume: The gases combine in a simple ratio by volume, when they are kept at constant temperature and pressure.

The correct answer is ​Bose-Einstein condensate.

Key Points

• Matters are generally categorized into 3 states:
  • Solid: Particles are held very close to each other and can't move. 
  • Liquid: Particles are close to each other but they can move around. 
  • Gas: Particles are far from each other as compared to those present in solid or liquid states and their movement is easy and fast. 
• Two more states are discovered under extreme circumstances:
  • Plasma: A superheated matter, so hot that the electrons are ripped away from the atoms forming an ionized gas. 
  • Bose-Einstein Condensate: A group of atoms cooled to absolute zero temperature(-273.15 ^oC).

Additional Information