MCQs Preparation - Page 5 of 65

If i, j and k are unit vectors along x-axis, y axis and z axis then i.j = j.k = i.k =

A. 0
B. 1/2
C. 1
D. none of these

Answer

A. 0

In the case of unit vectors i, j, and k representing the x, y, and z axes respectively, then i.j = j.k = i.k = 0.

Here’s why:

The dot product (represented by .) of two vectors calculates the magnitude of their projection onto each other.
Since i, j, and k are orthogonal (perpendicular) unit vectors, their projections onto each other will be zero.
Imagine a vector along the x-axis (i) and another along the y-axis (j). Projecting i onto j would result in a zero vector because i has no component in the y-direction. Similarly, projecting j onto i or any other two unit vectors will result in zero.

Therefore, the dot product of any two of these unit vectors will be 0.

If i, j and k are unit vectors along x-axis, y axis and z axis then i.j = j.k = i.k = Read More »

Unit of intensity of sound

A. Watt/m²
B. Watt/m⁻²
C. decibel
D. none of these

Answer

C. decibel

The unit of intensity of sound is C. decibel (dB). It measures the magnitude of sound energy per unit area in a logarithmic scale relative to a reference intensity. So, the correct answer is C. decibel.

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M.K.S unit of pressure

A. Pascal
B. Atmosphere
C. Torr
D. All of these

Answer

A. Pascal

The M.K.S (meter-kilogram-second) unit of pressure is A. Pascal. So, the correct answer is A. Pascal.

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What is the unit of energy?

A. Joule
B. Watt
C. Newton
D. Joule.Second

Answer

A. Joule

The SI unit of energy is Joule. So the answer is A. Joule.

Watt is the unit of power, not energy. Newton is the unit of force. Joule.sec is not a standard unit of energy.

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Magnetic Q.No. specifies:

A. Size of orbital
B. Shape of orbital
C. Orientation of orbital
D. Nuclear stability

Answer

C. Orientation of orbital

The magnetic quantum number (m_l) specifies:

C. Orientation of orbital

Here’s a breakdown of the quantum numbers and their specifications:

Principal quantum number (n): This specifies the energy level or shell of the electron.
Azimuthal quantum number (l): This specifies the subshell of the electron (s, p, d, f). It’s related to the shape of the orbital.
Magnetic quantum number (m_l): This specifies the orientation of the orbital within a subshell. Since orbitals of the same subshell have the same shape but may have different orientations in space, m_l helps distinguish them.
Spin quantum number (m_s): This specifies the spin of the electron along a chosen axis (usually +1/2 or -1/2).

So, the magnetic quantum number focuses on how an orbital is oriented in space, not its size or nuclear stability.

Magnetic Q.No. specifies: Read More »

The elements required to the soil in small amounts are called:

A. Micronutrients
B. Macronutrients
C. Meganutrients
D. Microscopic

Answer

A. Micronutrients

Micronutrients are essential for plant growth, even though they are needed in much smaller quantities compared to macronutrients. They play various roles in plant physiology, but only a tiny amount is sufficient. Examples of micronutrients include boron, copper, iron, and zinc.

Here’s a breakdown of the other options:

B. Macronutrients: These are elements required by plants in relatively large amounts. Examples include nitrogen, phosphorus, and potassium.
C. Meganutrients: This term is not a standard scientific term used in soil science.
D. Microscopic: Microscopic refers to the size of something being very small and needing a microscope to see. While some micronutrients may have microscopic particles, it doesn’t describe their function in the soil.

The elements required to the soil in small amounts are called: Read More »

The maximum concentration of substrate above which increase of substrate concentration does not increase the rate of reaction is called _______ of enzymes with substrate.

A. Termination
B. Saturation
C. Fluctuation
D. Maximum Optimation

Answer

B. Saturation

Enzymes are biological catalysts that accelerate the rate of chemical reactions. As the concentration of substrate increases, the rate of the reaction also increases due to more frequent collisions between enzyme and substrate molecules. However, there’s a limit:

Saturation: At a certain point, all the active sites of the enzyme molecules become occupied by substrate molecules. Increasing the substrate concentration further won’t affect the reaction rate because there are no free enzyme molecules available to bind with the additional substrate. This maximum concentration of substrate is called the saturation concentration.

The other options don’t accurately describe this concept:

Termination: Termination refers to the final step in a reaction pathway, not the limitation of substrate binding.
Fluctuation: Fluctuation implies random variations, not the specific point of maximum binding.
Maximum Optimation: This term isn’t commonly used in enzyme kinetics.

The maximum concentration of substrate above which increase of substrate concentration does not increase the rate of reaction is called _______ of enzymes with substrate. Read More »

An alkyl halide reacts with aqueous KOH solution to give an:

A. Aldehyde
B. Alkane
C. Alcohol
D. Acid

Answer

C. Alcohol

The reaction of an alkyl halide with aqueous KOH solution typically results in the formation of an alcohol.

Here’s why:

Alkyl halide: This represents a molecule where a halogen atom (Cl, Br, I, or F) is bonded to an alkyl group (a hydrocarbon chain).
Aqueous KOH solution: This refers to potassium hydroxide (KOH) dissolved in water. KOH acts as a strong base, with the OH⁻ ion being the nucleophile (electron-rich species) that attacks the alkyl halide.

In the reaction, the nucleophilic OH⁻ ion attacks the carbon atom bonded to the halogen in the alkyl halide. The halogen atom leaves as a halide ion (Cl⁻, Br⁻, I⁻, or F⁻), and a new C-O bond is formed, creating an alcohol.

Therefore, the answer is:

C. Alcohol

An alkyl halide reacts with aqueous KOH solution to give an: Read More »

2,4,6 – trinitrotoluene is abbreviated as:

A. TNA
B. TAN
C. TNT
D. NTT

Answer

C. TNT

TNT is the most common and widely recognized abbreviation for 2,4,6-trinitrotoluene. It’s used in various contexts, including chemistry, explosives engineering, and military applications.

2,4,6 – trinitrotoluene is abbreviated as: Read More »

The elements in which ‘d’ or ‘f’ orbitals are incomplete either in the atomic state or in their common ions are called:

A. Trans uranium elements
B. Transition elements
C. Lanthanides
D. Actinides

Answer

B. Transition elements

Transition elements: These elements (groups 3-12 in the periodic table) have incompletely filled d-orbitals in either their atomic state or in their common ions. This incomplete filling of d-orbitals contributes to their characteristic properties, including variable oxidation states, ability to form colored compounds, and involvement in coordination complexes.

The elements in which ‘d’ or ‘f’ orbitals are incomplete either in the atomic state or in their common ions are called: Read More »