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The correct answer is 35.

Key Points

• The mass number of an atom is calculated by summing the number of protons and neutrons in its nucleus.
• In this case, the atom has 17 protons and 18 neutrons.
• The formula for the mass number (A) is A = Number of Protons + Number of Neutrons.
• Therefore, the mass number of this atom is 17 + 18 = 35.

Additional Information

• Atomic Number
• The atomic number is the number of protons in the nucleus of an atom.
• It determines the chemical properties of an element and its place in the periodic table.
• For this atom, the atomic number is 17, indicating it is chlorine (Cl).
• Isotopes
• Isotopes are variants of a particular chemical element that have different numbers of neutrons.
• Chlorine has two stable isotopes: Cl-35 and Cl-37.
• Isotopes have the same atomic number but different mass numbers.
• Neutrons
• Neutrons are neutral particles found in the nucleus of an atom.
• They contribute to the mass of the atom but do not affect its chemical properties.
• The number of neutrons in this atom is 18.
• Electrons
• Electrons are negatively charged particles orbiting the nucleus of an atom.
• In a neutral atom, the number of electrons equals the number of protons.
• For this atom, there are 17 electrons.

The Correct answer is Both a and b.

Key Points

• The separation of H+ ions from HCl molecules indeed cannot occur in the absence of water. Water is necessary to facilitate the dissociation process.
• Hydrogen ions in an aqueous solution are always shown as H+ (aq) or H3O+ (hydronium ion). This is because hydrogen ions cannot exist freely in water; they combine with water molecules to form hydronium ions.
• When an acid like HCl is dissolved in water, it dissociates into H+ (aq) and Cl- (aq), demonstrating the necessity of water for this process.
• The correct representation of hydrogen ions in water as H+ (aq) or H3O+ ensures a more accurate depiction of their behavior in solution.
• Both statements are correct and together they provide a comprehensive understanding of the behavior of acids in water.

 Additional Information

• Hydronium Ion (H3O+)
• The hydronium ion is formed when a water molecule accepts a hydrogen ion (proton).
• It plays a key role in the chemistry of acids and bases in aqueous solutions.
• Hydronium ions are responsible for the acidic properties of solutions.
• Dissociation in Water
• Dissociation is the process by which molecules split into smaller particles such as ions.
• This process is crucial in understanding the behavior of acids, bases, and salts in water.
• Water acts as a solvent and facilitates the dissociation of ionic compounds.

The correct answer is Position of the metals in the reactivity series.

Key Points

• In a displacement reaction, the reactivity of the metals involved plays a crucial role.
• The reactivity series is an arrangement of metals in order of their reactivity, from most reactive to least reactive.
• A more reactive metal can displace a less reactive metal from its compound.
• This is because the more reactive metal has a greater tendency to lose electrons and form positive ions.
• For example, zinc can displace copper from copper sulfate solution because zinc is higher in the reactivity series than copper.

 Additional Information

• Temperature of the reaction
• While temperature can affect the rate of reaction, it does not determine whether one metal will displace another.
• Displacement reactions are more influenced by the reactivity of the metals involved.
• Size of the metal atoms
• The size of metal atoms does not play a significant role in displacement reactions.
• It is the reactivity and ability to lose electrons that matter more in these reactions.
• Concentration of the compound
• While the concentration of the compound can affect the rate of a reaction, it does not determine the displacement of metals.
• The ability to displace another metal is primarily dependent on the relative reactivity of the metals.

The correct answer is 4.

Key Points

• Saturated compounds are organic molecules containing only single bonds between carbon atoms.
• C2H6 (ethane) is a saturated compound with single bonds only.
• C3H8 (propane) is also saturated, containing only single bonds.
• C4H10 (butane) is a saturated compound with single carbon-carbon bonds.
• C2H4 (ethylene) is unsaturated because it contains a double bond between carbon atoms.

Additional Information

• Alkanes:
• Alkanes are hydrocarbons with only single covalent bonds between carbon atoms.
• They follow the general formula C_nH_2n+2.
• Examples: Methane (CH₄), Ethane (C₂H₆), Propane (C₃H₈).
• Alkenes:
• Alkenes are hydrocarbons containing at least one double bond between carbon atoms.
• They follow the general formula C_nH_2n.
• Examples: Ethylene (C₂H₄), Propylene (C₃H₆).
• Saturation in Organic Chemistry:
• Saturation refers to the presence of single bonds between carbon atoms in a compound.
• Saturated compounds are typically less reactive than unsaturated compounds.
• Hydrocarbons:
• Hydrocarbons are organic compounds consisting entirely of hydrogen and carbon.
• They can be classified into alkanes, alkenes, alkynes, and aromatic hydrocarbons based on the types of bonds they contain.

The correct answer is Option 4.

Key Points

• Reactivity Series: Zinc is more reactive than copper, and lead is also more reactive than copper. This follows the order of reactivity in the metal reactivity series.
• Zinc Reactivity: Zinc can displace copper from its compounds due to its higher reactivity.
• Lead Reactivity: Lead, although less reactive than zinc, is still more reactive than copper.
• Iron and Copper Sulphate Reaction: An iron nail dipped in copper sulphate solution will turn brownish-red due to the deposition of copper, not yellow.

Additional Information

• Metal Reactivity Series: This series ranks metals from highest to lowest reactivity. Elements like potassium and sodium are at the top, while gold and platinum are at the bottom.
• Displacement Reactions: More reactive metals can displace less reactive metals from their compounds in aqueous solutions.
• Copper Sulphate Solution: It is a blue solution commonly used in school experiments to demonstrate displacement reactions.
• Iron and Copper Reaction: When iron reacts with copper sulphate, iron displaces copper, forming iron sulphate and copper metal, which deposits on the iron surface.
• Color Changes in Reactions: The color change in chemical reactions involving transition metals can often indicate the formation of different compounds or the deposition of metals.

The correct answer is 2) i - b, ii - c, iii - a, iv - d.

Key Points

• Ketone uses the suffix -one indicating the presence of a carbonyl group (C=O).
• Alkene uses the suffix -ene indicating the presence of a carbon-carbon double bond (-C=C-).
• Aldehyde uses the suffix -al indicating the presence of a formyl group (-CHO).
• Carboxylic acid uses the suffix -oic acid indicating the presence of a carboxyl group (-COOH).

Additional Information

• Keto Group (C=O):
• Found in ketones, characterized by the carbonyl group bonded to two carbon atoms.
• Example: Propanone (acetone), the simplest ketone.
• Alkene Group (-C=C-):
• Alkenes are hydrocarbons with at least one carbon-carbon double bond.
• Example: Ethene (ethylene), used in the production of polyethylene.
• Formyl Group (-CHO):
• Found in aldehydes, characterized by a carbonyl group bonded to at least one hydrogen atom.
• Example: Methanal (formaldehyde), used in the production of resins.
• Carboxyl Group (-COOH):
• Found in carboxylic acids, characterized by a carbonyl and hydroxyl group attached to the same carbon.
• Example: Ethanoic acid (acetic acid), a key component of vinegar.

The correct answer is Manganese (Mn).

Key Points

• Manganese (Mn) reacts with very dilute nitric acid to evolve hydrogen gas.
• When dilute nitric acid is used, it acts as a typical acid releasing hydrogen gas.
• Manganese is a transition metal with the atomic number 25.
• Unlike other metals, when reacted with very dilute nitric acid, manganese releases hydrogen gas instead of producing nitrogen oxides.
• In most cases, nitric acid acts as a strong oxidizing agent, but in its dilute form, it can facilitate the release of hydrogen gas with certain metals.

 Additional Information

• Aluminium (Al)
• Aluminium reacts with nitric acid to form a passive oxide layer, preventing the release of hydrogen gas.
• This passive layer makes aluminium resistant to further reaction with nitric acid.
• Iron (Fe)
• Iron reacts with nitric acid, but instead of releasing hydrogen gas, it typically forms iron nitrate (Fe(NO₃)₃) and nitrogen oxides (NO or NO₂).
• Iron does not release hydrogen gas when reacted with nitric acid due to the oxidizing nature of nitric acid.
• Zinc (Zn)
• Zinc reacts with nitric acid to form zinc nitrate (Zn(NO₃)₂) and nitrogen oxides (NO or NO₂), rather than releasing hydrogen gas.
• Like iron, the reaction of zinc with nitric acid results in the formation of nitrogen oxides due to the strong oxidizing properties of nitric acid.

The correct answer is Atoms consist of a positively charged nucleus and negatively charged electrons..

Key Points

• Rutherford's gold foil experiment demonstrated that atoms have a small, dense, positively charged nucleus.
• Most of the atom's volume is empty space, with electrons orbiting the nucleus.
• Only a few alpha particles were deflected, indicating that the nucleus occupies a very small region of the atom.
• The experiment disproved the earlier plum pudding model proposed by J.J. Thomson, which suggested a uniform positive charge.
• The nucleus contains protons and neutrons, while electrons are located outside the nucleus.

Additional Information

• Alpha Particles:
• Alpha particles are positively charged particles consisting of two protons and two neutrons.
• They were used in Rutherford's experiment to probe the structure of the atom.
• Nucleus:
• The nucleus is the dense central part of an atom, containing protons and neutrons.
• It accounts for almost all the mass of the atom but occupies only a tiny fraction of its volume.
• Electron Cloud:
• The electron cloud is the region surrounding the nucleus where electrons are likely to be found.
• Electrons are negatively charged and move rapidly around the nucleus.
• Plum Pudding Model:
• Proposed by J.J. Thomson, it suggested that atoms were made up of electrons scattered within a "soup" of positive charge.
• This model was refuted by Rutherford's gold foil experiment.

Correct answer: Option 2) complement 

 Key Points

• "Complement" is the correct spelling.
• "Preceade" is an incorrect spelling of "precede".
• "Represant" is an incorrect spelling of "represent".
• "Mechinary" is an incorrect spelling of "machinery".

Therefore, the correctly spelt word is "complement". 

 Additional Information

• "Precede" means to come or go before something else in time or order.
• "Represent" means to act or speak on behalf of someone or something else.
• "Machinery" means the system of machines, parts, and tools used in a factory or other industrial operation.

The correct answer is "Option 3" i.e. 'is'.

 Key Points

• This sentence is centered around verb agreement with quantifiers. The phrase 'a lot of work' is treated as singular, since 'work' is an uncountable noun here.
• An example sentence would be: "A lot of effort has gone into completing this project."
• The correct term 'is' (है) aligns with the singular context- 'a lot of work'.

Therefore, the correct answer is - Option 3 "is".

 Additional Information

• 'Are' is incorrect as it's used with plural nouns or pronouns.
• 'Were' does not fit here, as it's the past tense of the plural form of the verb 'be'.
• 'Have' does not align with 'a lot of work', which is a singular uncountable noun.