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Chemistry · Question 731
What happens when an opaque object is placed in the path of cathode rays?
The rays are absorbed completely
A sharp shadow is produced
The rays pass through unchanged
The rays split into a spectrum
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Correct answer: B
A sharp shadow is produced
Cathode rays travel approximately in straight lines, so an opaque obstacle casts a sharp shadow.
Chemistry · Question 732
The nature of cathode rays remains the same when which discharge-tube component is changed?
The gas or electrode material
The electric charge on the rays
The electron mass
The direction of the electric field
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Correct answer: A
The gas or electrode material
Cathode rays are electrons; their nature does not depend on the gas or electrode material used.
Chemistry · Question 733
Why is the gas pressure reduced in a cathode-ray discharge tube?
To let the gas conduct electricity
To increase gas density
To stop ion formation
To condense the gas
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Correct answer: A
To let the gas conduct electricity
At sufficiently low pressure, ionization permits a discharge and the production of cathode rays.
Chemistry · Question 734
A light pinwheel placed in the path of cathode rays rotates. This demonstrates that cathode rays possess:
Momentum
Positive charge
No mass
Only wave properties
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Correct answer: A
Momentum
The rays transfer momentum to the pinwheel, showing particle behaviour.
Chemistry · Question 735
Deflection of cathode rays toward a positively charged plate shows that they are:
Positively charged
Negatively charged
Neutral
Electromagnetic waves
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Correct answer: B
Negatively charged
Opposite charges attract, so attraction to the positive plate identifies a negative charge.
Chemistry · Question 736
In the absence of external fields, cathode rays travel in:
Circular paths
Curved paths
Zigzag paths
Straight lines
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Correct answer: D
Straight lines
Cathode rays propagate in straight lines unless electric or magnetic fields deflect them.
Chemistry · Question 737
The internuclear separation at which the potential energy of two bonded atoms is minimum is called:
Ionization distance
Equilibrium bond distance
Collision diameter
Atomic radius
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Correct answer: B
Equilibrium bond distance
A stable bond has its minimum potential energy at the equilibrium bond length.
Chemistry · Question 738
One thermochemical calorie is approximately equal to:
0.239 J
1.00 J
4.184 J
41.84 J
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Correct answer: C
4.184 J
The standard conversion is 1 cal = 4.184 J.
Chemistry · Question 739
A force of one newton acting through one metre does how much work?
One watt
One joule
One pascal
One coulomb
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Correct answer: B
One joule
Work equals force times displacement, so 1 N × 1 m = 1 J.
Chemistry · Question 740
Liquid water in a closed container at constant temperature establishes which kind of equilibrium with its vapour?
Static
Dynamic
Irreversible
Mechanical
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Correct answer: B
Dynamic
Evaporation and condensation continue at equal rates in dynamic equilibrium.