Answer:
a solution color becoming less intense due to dilution- is not an evidence of a chemical reaction
bubbles (gas formation) - evidence of a chemical reaction
explosion or fire - evidence of a chemical reaction
changes in color- evidence of a chemical reaction
precipitation- evidence of a chemical reaction
changes in temperature - evidence of a chemical reaction
a solid liquifying - is not an evidence of a chemical reaction
solution colors mixing - is not an evidence of a chemical reaction
Explanation:
A chemical change is not easily reversible and yields new substances. It is often accompanied by a loss or gain of heat.
In the answer section, i have shown some evidences that lead us to conclude that a chemical reaction has taken place. The occurrence of a chemical change often goes with the formation of new substances as earlier stated and any of these signs may accompany the process.
For instance, when a metal is dropped in dilute acid solution, bubble of hydrogen gas indicates that a chemical reaction has taken place.
We will use the expression for freezing point depression ∆Tf
∆Tf = i Kf m
Since we know that the freezing point of water is 0 degree Celsius, temperature change ∆Tf is
∆Tf = 0C - (-3°C) = 3°C
and the van't Hoff Factor i is approximately equal to 2 since one molecule of KCl in aqueous solution will produce one K+ ion and one Cl- ion:
KCl → K+ + Cl-
Therefore, the molality m of the solution can be calculated as
3 = 2 * 1.86 * m
m = 3 / (2 * 1.86)
m = 0.80 molal
<u>Answer:</u> The half life of the reaction is 1190.7 seconds
<u>Explanation:</u>
The equation used to calculate rate constant from given half life for first order kinetics:
where,
k = rate constant of the reaction = 
= half life of the reaction = ?
Putting values in above equation, we get:
Hence, the half life of the reaction is 1190.7 seconds
Answer:
Dual nature of matter is an important concept in JEE physics and is basically the study of different nature that a matter possesses or exhibits. ... Hence, the matter is said to possess dual nature, i.e., it has both the properties of a particle and as well as a wave.
Answer:
Explanation:
The work function of the sodium= 495.0 kJ/mol
It means that
1 mole of electrons can be removed by applying of 495.0 kJ of energy.
Also,
1 mole = 
So,
electrons can be removed by applying of 495.0 kJ of energy.
1 electron can be removed by applying of 
of energy.
Energy required = 
Also,
1 kJ = 1000 J
So,
Energy required = 
Also, 
Where,
h is Plank's constant having value 
c is the speed of light having value 
So,
Also,
1 m = 10⁻⁹ nm
So,
