Explanation:
A chemical reaction is defined as the reaction in which bonds between the reactants either break or form which leads to the formation of a new substance.
For example, 
So, when we drop a sodium metal into water then it produces a frizzing sound which shows the metal is reacting with water.
We know that when two aqueous solutions chemically react with each other then it may lead to the formation of an insoluble substance which is known as precipitate.
This means that formation of a precipitate is also a chemical reaction.
Thus, we can conclude that following are the statements which show evidence for a chemical reaction.
- Dropping sodium metal into water produces fizzing.
- Mixing two aqueous solutions produces a precipitate.
Answer:
25 g/hr
Explanation:
Remember that the rate of reaction refers to the rate at which reactants are used up or or the rate at which products appear.
Hence;
Rate of reaction = mass of reactant used up/time taken
Mass of reactant used up= 2g
Time taken = 5 minutes or 0.08 hours
Rate of reaction = 2g/0.08 hours = 25 g/hr
Answer:
The kinetic energy of the two stones is 320 J
Explanation:
Kinetic energy is the energy that a body possesses due to its movement. So it is the capacity or work that allows an object to go from being at rest, or still, to moving at a certain speed.
In other words, the kinetic energy of an object is that which is produced due to its motion and depends on its mass and velocity as follows:

where the kinetic energy Ec is measured in joules (J), the mass m is measured in kilograms (kg) and the velocity v in meters/second (m/s).
In this case you know that a 20 kg curling stone is sliding in a positive direction at 4 m/s. So:
Replacing you have:

Ec₁= 160 J
A second curling stone slides at the same speed but in the opposite direction. So:
Replacing you have:

Ec₂= 160 J
The kinetic energy of the two stones is calculated as:
Ec= Ec₁ + Ec₂
Ec= 160 J + 160 J
Ec= 320 J
<u><em>The kinetic energy of the two stones is 320 J</em></u>
Hydrochloric acid is polar which means it has stronger bonds between it's molecules, unlike diatomic fluorine that is non-polar and has weaker bonds. That's why it has a higher boiling point.