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a year ago

Class 11th Redox Reactions

Explain redox reactions on the basis of electron transfer. Give suitable examples.

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alok kumar singh

Contributor-Level 10

This is a Long answer type question as classified in NCERT Exemplar

The given reaction is a redox change.

2Na (s)+H₂ (g)→2NaH (s)

The half reaction is:

2Na (s)→2Na⁺ (g)+2e^-

The other half reaction is:

H₂ (g)+2e^-→2H^- (g)

This splitting of the reaction into two half-reactions automatically reveals here that sodium is oxidized, and hydrogen is reduced. Any substance which loses electron is oxidized and gains electron is reduced hence is the case of sodium and hydrogen atoms respectively. Hence, the complete reaction is a redox change.

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New answer posted

a year ago

Class 11th The S Block Elements

Two balls of same mass and carrying equal charge are hung by threads of length $l$ from a fixed support. At electrostatic equilibrium, assuming that angles made by each thread is small, the separation, $x$ between the balls is proportional to:

(a.) $l$

(b.) $l^{2}$

(c.) $l^{2 / 3}$

(d.) $l^{1 / 3}$

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alok kumar singh

Contributor-Level 10

mg In equilibrium, $F_{} = θ$

$= θ$

$θ = \frac{F_{}}{} = \frac{^{2}}{4 π \in_{0}^{2} *}$

also $θ \approx ? = \frac{/ 2}{l}$

Hence, $\frac{}{2 l} = \frac{^{2}}{4 π \in_{0}^{2} *}$

$\Rightarrow^{3} = \frac{2^{2} p}{4 π ε_{0}}$

$= {(\frac{^{2} l}{2 π \in_{0}})}^{1 / 3}$

Therefore $\propto l^{1 / 3}$

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New question posted

a year ago

Class 11th The S Block Elements

Based on the passage, which of the following best captures the meaning of HIF, or hypoxia-inducible factor?

A. It is a protein that increases inside the cell when the oxygen levels fall, helping the cell survive.
B. It inhibits oxygen carrying process in the body as the oxygen level increases inside the cell.
C. It enables cells to adapt quickly to the changing environment and helps in its survival.
D. It regulates the amount of oxygen available to the cell and the body during exercise.

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New question posted

a year ago

Class 11th The S Block Elements

Based on the passage, which of the following best captures the meaning of HIF, or hypoxia-inducible factor?

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New answer posted

a year ago

Class 11th The S Block Elements

Based on the passage, which of the following best captures the meaning of HIF, or hypoxia-inducible factor?

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alok kumar singh

Contributor-Level 10

Answer-A
Only first option clearly defines the meaning of HIF, by using the term 'protein'. Option C can be a characteristic but not a complete meaning. The meaning can be derived with the help of the following lines “When oxygen levels decrease, the HIF protein inhibits oxygen-consuming processes of the cells by altering the activity of numerous genes”.

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New answer posted

a year ago

Class 11th Systems of Particles and Rotational Motion

With reference to Fig. of a cube of edge a and mass m, state whether the following are true or false. (O is the centre of the cube.)

(a) The moment of inertia of cube about z-axis is I_z = I_x + I_y

(b) The moment of inertia of cube about z′ is I_z =I_z +ma²/2

(c) The moment of inertia of cube about z″ is I_z+ma²/2 (d) I_x = I_y

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Payal Gupta

Contributor-Level 10

This is a multiple choice type question as classified in NCERT Exemplar

a, b, d

a) according to the perpendicular axes theorem statement 1 is wrong

b) As z'|z so distance between them = a $\frac{\sqrt[]{2}}{2} = \frac{a}{\sqrt[]{2}}$

So according to parallel axes theorem I_z'=I_z+m (a/ $\sqrt[]{2}$ )²= I_z+ma²/2

Hence b is true

c) z' is not parallel to z hence Parallel axes does not applied so statement is false

d) as x and y axes are symmetrical . hence I_x=I_yso d is true

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New answer posted

a year ago

Class 11th Systems of Particles and Rotational Motion

Figure 7.5 shows a lamina in x-y plane. Two axes z and z′ pass perpendicular to its plane. A force F acts in the plane of lamina at point P as shown. Which of the following are true? (The point P is closer to z′-axis than the z-axis.)

(a) Torque τ caused by F about z axis is along ˆ -k.

(b) Torque τ′ caused by F about z′ axis is along ˆ -k.

(c) Torque τ caused by F about z axis is greater in magnitude than that about z axis.

(d) Total torque is given be τ = τ + τ′.

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Payal Gupta

Contributor-Level 10

This is a multiple choice type question as classified in NCERT Exemplar

b, c

a) When r>r'

Torque about z-axis t=r $*$ F

b) t'=r' $* F$ which is along negative z axis

c) t_z=Fr = magnitude of torque about z axis where r is perpendicular between F and z axis so torque along positive z axis is greater than negative z axis.

d) We are always calculating resultant torque about common axis. Hence total torque not equal to combination of torque along both axis of z, because they are not on common axis.

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New answer posted

a year ago

Class 11th Systems of Particles and Rotational Motion

The net external torque on a system of particles about an axis is zero. Which of the following are compatible with it ?

(a) The forces may be acting radially from a point on the axis.

(b) The forces may be acting on the axis of rotation.

(c) The forces may be acting parallel to the axis of rotation.

(d) The torque caused by some forces may be equal and opposite to that caused by other forces

0 Follower 9 Views

Payal Gupta

Contributor-Level 10

This is a multiple choice type question as classified in NCERT Exemplar

a, b, c, d

As we know torque = r $*$ F = rFsin $θ$

a) when forces act radially angle =0 hence torque =0

b) when forces are acting on the axis of rotation r=0 torque=0

c) when forces acting parallel to the axis of rotation angle =0 so torque =0

d) when torque by forces are equal and opposite torque net = t₁-t₂=0

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New answer posted

a year ago

Class 11th Systems of Particles and Rotational Motion

Figure shows two identical particles 1 and 2, each of mass m, moving in opposite directions with same speed v along parallel lines. At a particular instant, r₁ and r₂ are their respective position vectors drawn from point A which is in the plane of the parallel lines.

Choose the correct options:

(a) Angular momentum l₁ of particle 1 about A is I = mvd₁

(b) Angular momentum l2 of particle 2 about A is l₂= mvr₂

(c) Total angular momentum of the system about A is l= mv(r₁+r₂)

(d) Total angular momentum of the system about A is l = mv(d₂-d₁)⊗ represents a unit vector coming out of the page. ⊗ represents a unit vector going i

...more

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Payal Gupta

Contributor-Level 10

This is a multiple choice type question as classified in NCERT Exemplar

(a), (b)As we know L= r $*$ p where r is position vector and p is the linear momentum . the direction of L is perpendicular to both r and p by right hand rule.

For particle 1

I₁=r_{1
$*$}mv is out of the plane of the paper and perpendicular to r₁ and p . similarly I₂=r_{2
$*$}m (-v) is into the plane of the paper and perpendicular to r₂ and -p.

Hence total angular momentum

L= L₁+L₂= I₁=r_{1
$*$}mv+ (r_{2
$*$}m (-v)

L= mvd₁-mvd₂ as d₂>d₁

So total angular momentum will be inwards so I = l = mv (d₂-d₁)⊗

L= mvd₁-mvd₂ as d₂>d₁

So total angular momentum will be inwards so I = l = mv (d₂-d₁)?

...more

This is a multiple choice type question as classified in NCERT Exemplar

(a), (b)As we know L= r $*$ p where r is position vector and p is the linear momentum . the direction of L is perpendicular to both r and p by right hand rule.

For particle 1

I₁=r_{1
$*$}mv is out of the plane of the paper and perpendicular to r₁ and p . similarly I₂=r_{2
$*$}m (-v) is into the plane of the paper and perpendicular to r₂ and -p.

Hence total angular momentum

L= L₁+L₂= I₁=r_{1
$*$}mv+ (r_{2
$*$}m (-v)

L= mvd₁-mvd₂ as d₂>d₁

So total angular momentum will be inwards so I = l = mv (d₂-d₁)⊗

L= mvd₁-mvd₂ as d₂>d₁

So total angular momentum will be inwards so I = l = mv (d₂-d₁)?

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New answer posted

a year ago

Class 11th Systems of Particles and Rotational Motion

Choose the correct alternatives:

(a) For a general rotational motion, angular momentum L and angular velocity ω need not be parallel.

(b) For a rotational motion about a fixed axis, angular momentum L and angular velocity ω are always parallel.

(c) For a general translational motion , momentum p and velocity v are always parallel.

(d) For a general translational motion, acceleration a and velocity v are always parallel.

0 Follower 7 Views

Payal Gupta

Contributor-Level 10

This is a multiple choice type question as classified in NCERT Exemplar

(a), (c) For general rotational motion where axis of rotation is not symmetric . angular momentum L and angular velocity w need not be parallel. For general translational motion momentum p=mv hence p and v are always parallel.

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