Q1 .what happen when acetylene is heated with silver powder
When acetylene (C2H2) is heated with silver powder (Ag), a reaction may occur between the two substances. The reaction between acetylene and silver powder is known as the acetylene silver mirror reaction.
In this reaction, the acetylene gas is oxidized by the silver powder, resulting in the deposition of elemental carbon (soot) and the formation of a silver mirror on the surface of the silver powder. The reaction can be represented by the following equation:
2Ag + C2H2 → Ag2C2H2 + C
The silver mirror forms due to the reduction of silver ions (Ag+) present in the silver powder to elemental silver (Ag). The acetylene gas serves as a reducing agent in this process. The reaction is often carried out by mixing acetylene gas with the silver powder in a sealed container and heating the mixture.
It is worth noting that the acetylene silver mirror reaction is primarily a demonstration experiment used in chemistry and is not a practical synthetic route to produce specific compounds. The reaction is known for its visually striking result of a reflective silver surface, which forms on the inner surface of the reaction container.
In short, when acetylene is heated with silver powder, a reaction occurs where the acetylene gas is oxidized by the silver powder. This leads to the formation of a silver mirror on the surface of the silver powder and the deposition of elemental carbon. The reaction is primarily used as a demonstration and results in a visually striking silver mirror effect.
Q2. Define redox reactions. Balance the following redox reactions by oxidation number method. Zn + HNO2 -> Zn(NO3)2 + NO + H2O
Redox reactions, short for reduction-oxidation reactions, are chemical reactions in which there is a transfer of electrons between species. In these reactions, one species undergoes oxidation by losing electrons (increasing its oxidation number), while another species undergoes reduction by gaining those electrons (decreasing its oxidation number).
Now let's balance the given redox reaction, Zn + HNO2 -> Zn(NO3)2 + NO + H2O, using the oxidation number method:
Assign oxidation numbers to each element in the equation:
Zn: 0 (unchanged)
H: +1
N: +3 (in HNO2) and +5 (in NO3 and NO)
O: -2 (in HNO2 and NO3) and -2 (in H2O)
Identify the elements undergoing oxidation and reduction:
Zn is being oxidized (its oxidation number increases from 0 to +2).
N is being reduced (its oxidation number decreases from +3 to +2).
Write the half-reactions for oxidation and reduction:
Oxidation half-reaction: Zn -> Zn^2+ (oxidation number increases from 0 to +2).
Reduction half-reaction: HNO2 -> NO + H2O (N undergoes reduction from +3 to +2).
Balance the atoms other than hydrogen and oxygen in each half-reaction:
Oxidation: Zn -> Zn^2+ (already balanced)
Reduction: HNO2 -> NO + H2O
2HNO2 -> 2NO + 2H2O (balanced hydrogen and oxygen)
Balance the oxygen atoms by adding water (H2O) molecules:
Oxidation: Zn -> Zn^2+ (no oxygen present)
Reduction: 2HNO2 -> 2NO + 2H2O (already balanced)
Balance the hydrogen atoms by adding H+ ions:
Oxidation: Zn -> Zn^2+ (no hydrogen present)
Reduction: 2HNO2 -> 2NO + 2H2O (already balanced)
Balance the charges by adding electrons (e^-):
Oxidation: Zn -> Zn^2+ + 2e^-
Reduction: 2HNO2 + 2e^- -> 2NO + 2H2O
Make the number of electrons equal in both half-reactions:
Multiply the oxidation half-reaction by 2:
2Zn -> 2Zn^2+ + 4e^-
Combine the two half-reactions, canceling out the electrons:
2Zn + 2HNO2 + 2e^- -> 2Zn^2+ + 4e^- + 2NO + 2H2O
Simplify the equation:
2Zn + 2HNO2 -> 2Zn^2+ + 2NO + 2H2O
The balanced equation using the oxidation number method is:
2Zn + 2HNO2 -> 2Zn(NO3)2 + 2NO + 2H2O
Q3. what happen when phenol is heated with zinc dust
When phenol (C6H5OH) is heated with zinc dust (Zn), a reaction known as the Clemmensen reduction occurs. The reaction involves the reduction of the phenol molecule to form cyclohexane.
The Clemmensen reduction is a specific method used to convert carbonyl compounds, such as ketones and aldehydes, into hydrocarbons. In this case, phenol, which contains a hydroxyl group (-OH) attached to an aromatic ring, undergoes reduction to produce cyclohexane, a saturated hydrocarbon with a six-membered ring.
The reaction can be summarized as follows:
C6H5OH + Zn → C6H12 + ZnO
In this reaction, the zinc dust serves as a reducing agent, causing the removal of the oxygen atom from the phenol molecule. As a result, the aromatic ring of phenol is reduced, and cyclohexane is formed. Zinc oxide (ZnO) is produced as a byproduct.
It's important to note that the Clemmensen reduction is specific to carbonyl compounds and is not typically used to reduce phenols. Phenols usually undergo different types of reactions, such as electrophilic aromatic substitution or oxidation reactions. However, under specific conditions, heating phenol with zinc dust can lead to the Clemmensen reduction and the formation of cyclohexane.
Q4. define covalent bond with example
A covalent bond is a type of chemical bond formed between two atoms by sharing one or more pairs of electrons. In a covalent bond, atoms achieve a stable electron configuration by sharing electrons with each other rather than transferring them. Covalent bonds typically occur between nonmetal atoms.
Here's an example to illustrate a covalent bond:
Consider the formation of a covalent bond between two hydrogen (H) atoms:
Each hydrogen atom has one valence electron. Both hydrogen atoms require one more electron to achieve a stable electron configuration like helium (He) with two electrons in its outermost shell.
Instead of transferring electrons, the two hydrogen atoms can share their electrons to achieve a stable configuration. They form a covalent bond by sharing one pair of electrons.
The resulting molecule, known as hydrogen gas (H2), consists of two hydrogen atoms held together by a covalent bond. Each hydrogen atom contributes one electron to the shared pair, forming a stable electron configuration for both atoms.
The representation of the covalent bond between two hydrogen atoms can be shown using Lewis dot structures as follows:
H: ● ● :H
The dot represents a valence electron, and the pair of dots represents the shared pair of electrons forming the covalent bond.
In this example, both hydrogen atoms share one pair of electrons, fulfilling their electron requirements and achieving stability through a covalent bond.
In short, a covalent bond is a chemical bond formed when two nonmetal atoms share one or more pairs of electrons. It allows both atoms to achieve a stable electron configuration. For example, in a covalent bond between two hydrogen atoms, they share one pair of electrons to form a stable hydrogen gas molecule (H2).
Q5. among oxygen and nitrogen which has higher value and why
The question seems to be referring to the electronegativity values of oxygen and nitrogen. Electronegativity is a measure of an atom's tendency to attract electrons towards itself in a chemical bond.
On the Pauling scale, which is commonly used to express electronegativity values, oxygen has a higher electronegativity value than nitrogen. Oxygen has an electronegativity value of approximately 3.44, while nitrogen has an electronegativity value of approximately 3.04.
The higher electronegativity of oxygen is due to its smaller atomic size and higher effective nuclear charge compared to nitrogen. Oxygen has a greater ability to attract and hold onto electrons in a chemical bond, making it more electronegative.
It's important to note that electronegativity values are relative and can vary depending on the specific scale used. The values provided above are approximate and commonly accepted values on the Pauling scale.
In short, oxygen has a higher electronegativity value compared to nitrogen. This is because of its smaller atomic size and higher effective nuclear charge, which gives oxygen a greater ability to attract and hold onto electrons in a chemical bond.
Q6. define electrophile and Nucleophile: with suitable example of each in short
Electrophile:
An electrophile is an atom or molecule that seeks to accept or bond with an electron pair in a chemical reaction. Electrophiles are electron-deficient species that have a positive charge or partially positive charge. They are attracted to regions of high electron density. Electrophiles are often involved in reactions such as nucleophilic substitution or electrophilic addition.
Example: A common example of an electrophile is a carbocation (positively charged carbon atom) in organic chemistry. Carbocations are electron-deficient and can react with nucleophiles, such as negatively charged species or atoms with lone pairs of electrons.
Nucleophile:
A nucleophile is an atom or molecule that donates or shares an electron pair in a chemical reaction. Nucleophiles are electron-rich species that have a negative charge or possess lone pairs of electrons. They are attracted to regions of low electron density or positively charged species. Nucleophiles are often involved in reactions such as nucleophilic substitution or nucleophilic addition.
Example: One example of a nucleophile is the hydroxide ion (OH-) in organic chemistry. The hydroxide ion has a lone pair of electrons and can donate this electron pair to form a new bond with an electrophile, such as an alkyl halide in a nucleophilic substitution reaction.
In summary, electrophiles are electron-deficient species that seek to accept electron pairs, while nucleophiles are electron-rich species that donate or share electron pairs. They play crucial roles in various chemical reactions by participating in bond formation and breaking processes.
in short
In short, an electrophile is an electron-deficient species that seeks to accept or bond with an electron pair. A nucleophile, on the other hand, is an electron-rich species that donates or shares an electron pair. An example of an electrophile is a carbocation, while a hydroxide ion is an example of a nucleophile.
Q7. establish relationship between ph and poh
The relationship between pH and pOH is based on the concept of the pH scale, which is a measure of the acidity or alkalinity (basicity) of a solution.
The pH scale ranges from 0 to 14, where pH 7 is considered neutral, pH values below 7 indicate acidity, and pH values above 7 indicate alkalinity (basicity).
The pOH scale is the complementary scale to pH and is used to measure the concentration of hydroxide ions (OH-) in a solution. Similar to pH, pOH values range from 0 to 14.
The relationship between pH and pOH can be expressed mathematically using the equation:
pH + pOH = 14
This equation states that the sum of the pH and pOH values of a solution is always equal to 14. This means that if you know the pH of a solution, you can calculate the pOH using the equation above, and vice versa.
For example, if a solution has a pH of 3, you can calculate the pOH as follows:
pH + pOH = 14
3 + pOH = 14
pOH = 14 - 3
pOH = 11
Conversely, if you know the pOH of a solution, you can calculate the pH using the same equation.
This relationship between pH and pOH allows us to determine the acidity or alkalinity of a solution based on the concentration of either hydrogen ions (H+) for pH or hydroxide ions (OH-) for pOH.
Q7. why chloroform is stroed in dark color bottle
Chloroform (CHCl3) is often stored in dark-colored bottles to protect it from light. Light, especially ultraviolet (UV) light, can cause chemical reactions in chloroform and lead to its degradation.
Chloroform is sensitive to light and undergoes a photochemical reaction called photolysis when exposed to UV light. This reaction can result in the formation of harmful byproducts and decomposition of chloroform, leading to a decrease in its stability and effectiveness.
By storing chloroform in dark-colored bottles, such as amber or brown glass, the entry of light, particularly UV light, is minimized or prevented. The dark-colored glass bottles act as a barrier, reducing the exposure of chloroform to light and helping to maintain its stability over a longer period.
It is worth noting that chloroform should also be stored in a cool and well-ventilated area, away from heat sources or open flames, as it is a volatile and flammable liquid. Proper storage conditions, including the use of dark-colored bottles, help ensure the integrity and quality of chloroform for its intended use.
in very short
In very short, chloroform is stored in dark-colored bottles to protect it from light-induced degradation. Light, especially UV light, can cause chemical reactions in chloroform and reduce its stability and effectiveness. Dark-colored bottles act as a barrier, minimizing exposure to light and preserving chloroform's quality.
Q8. surface tension
Surface tension refers to the cohesive force present at the surface of a liquid, which causes the molecules at the surface to be more strongly attracted to each other than to the molecules in the bulk of the liquid. This attraction leads to the formation of a thin, elastic layer on the surface of the liquid. The surface tension of a liquid is responsible for various phenomena, such as the ability of insects to walk on water or the formation of droplets.
Q9 The Lewis structure WITH RULE
The Lewis structure of H2SO4, also known as sulfuric acid, can be determined by following a few steps:
Step 1: Count the total number of valence electrons.
H: 2 x 1 = 2 electrons
S: 1 x 6 = 6 electrons
O: 4 x 6 = 24 electrons
Total: 2 + 6 + 24 = 32 electrons
Step 2: Determine the central atom.
In H2SO4, the sulfur (S) atom is the central atom since it is the least electronegative element.
Step 3: Connect the outer atoms to the central atom with single bonds.
Connect the two hydrogen (H) atoms to the sulfur (S) atom with single bonds.
H-S-H
Step 4: Place the remaining electrons around the atoms to complete their octets.
Since each hydrogen atom only needs 2 electrons to complete its octet, they are already satisfied.
Place the remaining electrons around the sulfur (S) and oxygen (O) atoms. Start by placing them as lone pairs on the oxygen atoms and then distribute the remaining electrons to complete the octets of sulfur and oxygen.
mathematica
Copy code
O
//
H - S - O
\\
O
Step 5: Check if the central atom has an octet.
The sulfur atom (S) currently has 12 electrons around it (4 from the single bonds and 8 from the lone pairs). Since sulfur can expand its octet, it can accommodate more than 8 electrons. Therefore, the Lewis structure of H2SO4 is complete.
Note: The Lewis structure provided represents the arrangement of atoms and electrons in the molecule but does not depict the actual shape or geometry of the molecule.
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