Which of the following must be the same before and after a chemical reaction?
1 answer:
Answer: Option (D) is the correct answer.
Explanation:
A chemical reaction is defined as the reaction which causes change in chemical composition of a substance.
According to law of conservation of mass, mass can neither be created nor it can be destroyed. It can only be changed from one form to another.
For example,
Here, total mass of reactants = (1.008 + 35.453) g/mol = 36.461 g/mol
Whereas total mass of products = 36.461 g/mol
This shows that mass remains the same before or after the reaction.
Similarly, the number of atoms of the type involved will remains the same as no change in their nucleus is occurring.
Thus, we can conclude that the following must be the same before and after a chemical reaction.
- The sum of the masses of all substances involved.
- The number of atoms of the type involved.
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Answer:
200 nm is the thinnest film that produces a strong reflection for green light with a wavelength of 500 nm
Explanation:
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for thinnest film m=1
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Answer:
W = 1884J
Explanation:
This question is incomplete. The original question was:
<em>Consider a motor that exerts a constant torque of 25.0 N.m to a horizontal platform whose moment of inertia is 50.0kg.m^2 . Assume that the platform is initially at rest and the torque is applied for 12.0rotations . Neglect friction. </em>
<em> How much work W does the motor do on the platform during this process? Enter your answer in joules to four significant figures.</em>
The amount of work done by the motor is given by:
Where I = 50kg.m^2 and ωo = rad/s. We need to calculate ωf.
By using kinematics:
But we don't have the acceleration yet. So, we have to calculate it by making a sum of torque:
=>
Now we can calculate the final velocity:
Finally, we calculate the total work:
Since the question asked to "<em>Enter your answer in joules to four significant figures.</em>":
W = 1884J