light with any intensity above a certain frequency
light with any frequency below a certain intensity
light with any frequency above a certain intensity
The correct answer: (b) light with any intensity above a certain frequency
The explanation:
when Energy of a photon : E = hf
- The photoelectric effect works like this:
- If you shine light of high enough energy on to a metal, electrons will be emitted from the metal. Light below a certain threshold frequency, no matter how intense, will not cause any electrons to be emitted. Light above the threshold frequency, even if it's not very intense, will always cause electrons to be emitted.
Answer:
b
Explanation:
B. 0.20 m FeI3
C. 0.20 m K2SO4
D. 0.20 m C2H5OH
Answer:- D. 0.20 m
Explanations:- When a on volatile solute is added to a solvent then the boiling point of the solution increases(elevated) and we call it elevation in boiling point.
Elevation in boiling point is directly proportional to the molality of the solution and the Van't Hoff factor "i" which is the number of ions we get on dissociation.
The equation is written as:
where is the boiling point elevation constant.
We have all the aqueous solutions, so the boiling point elevation constant value will remain same for all of them. The molality for all the solutions is also same. So, elevation in boiling point will depend only on the value of Van't Hoff factor.
Lower is the value of "i", lower will be the boiling point and vice versa.
The question asks, which aqueous solution has the lowest boiling point. So, we nede to choose the one with the lowest value of "i".
i = 3
i = 4
i = 3
is a covalent molecule and so it does not dissociate to give the ions and hence the value of "i" for this is 1.
Comparing the "i" values for all the solutions, the least value is for ethyl alcohol means the boiling point of 0.20 m ethyl alcohol solution will be lowest.
So, the correct answer is D. 0.20 m .
the equation for calculating density is m÷v
Question 1 options:
Decreasing the volume of the reaction container.
Adding more particles of reactants.
Adding a chemical catalyst.
Increasing the temperature of the reaction.
Question 2 (1 point)
In this analogy, shrinking the hallways is analogous to:
Question 2 options:
Decreasing the volume of the reaction container.
Adding more particles of reactants.
Adding a chemical catalyst.
Increasing the temperature of the reaction.
Question 3 (1 point)
chemical catalyst helps change the rate of a chemical reaction by
Question 3 options:
Adding more reactants
Decreasing the activation energy
Increasing the activation energy
Adding more products
Question 4 (1 point)
In this analogy, shortening the passing periods is analogous to:
Question 4 options:
Decreasing the volume of the reaction container.
Adding more particles of reactants.
Adding a chemical catalyst.
Increasing the temperature of the reaction.
Question 5 (1 point)
In this analogy, hiring a matchmaker is analogous to:
Question 5 options:
Decreasing the volume of the reaction container.
Adding more particles of reactants.
Adding a chemical catalyst.
Increasing the temperature of the reaction.
Question 6 (1 point)
What are two conditions that must be met in order for a chemical reaction to take place?
Question 6 options:
Collisions with the proper orientation
Sufficient activation energy
Appropriate coefficient of friction
Both A and B
Both B and C
Answer:D - adding a catalyst
Explanation:
In this analogy, adding more students is analogous to adding more particles of reactants in a chemical reaction. Shrinking the hallways is analogous to decreasing the volume of the reaction container. A chemical catalyst helps change the rate of a chemical reaction by decreasing the activation energy.
Question 1: Adding more students in this analogy is analogous to adding more particles of reactants in a chemical reaction. Just like adding more students can increase the amount of activity and interactions in a classroom, adding more particles of reactants can increase the collision frequency and hence the reaction rate.
Question 2: Shrinking the hallways in this analogy is analogous to decreasing the volume of the reaction container in a chemical reaction. Just like shrinking the hallways restricts the movement of students, decreasing the volume of the reaction container restricts the movement of particles and increases the collision frequency.
Question 3: A chemical catalyst helps change the rate of a chemical reaction by decreasing the activation energy required for the reaction to occur. It provides an alternate reaction pathway with a lower activation energy, allowing more particles to have sufficient energy to react.
Question 4: Shortening the passing periods in this analogy is analogous to increasing the temperature of the reaction in a chemical reaction. Just like shortening the passing periods allows students to move faster and increases their chances of colliding, increasing the temperature of the reaction increases the kinetic energy of particles and enhances their collision frequency.
Question 5: Hiring a matchmaker in this analogy is analogous to adding a chemical catalyst in a chemical reaction. Just as a matchmaker facilitates the meeting of compatible people, a chemical catalyst facilitates the reaction between reactant particles, increasing the reaction rate.
Question 6: Two conditions that must be met for a chemical reaction to take place are collisions with the proper orientation and sufficient activation energy. Collisions between reactant particles must occur with the proper orientation to enable the formation of new chemical bonds, and these collisions must also have sufficient energy to overcome the activation energy barrier.
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