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.
1 elements
2 they have same number of valence electrons
3 period
Answer:
gravitational energy
Explanation:
It is gravitational (potential) energy because of the place that the rock holds in the gravitational field. It has <u>potential</u> to move downward, because of <u>gravity</u>.
<u>Answer:</u> The mass of solid NaOH required is 80 g
<u>Explanation:</u>
Equivalent weight is calculated by dividing the molecular weight by n factor. The equation used is:
where,
n = acidity for bases = 1 (For NaOH)
Molar mass of NaOH = 40 g/mol
Putting values in above equation, we get:
Normality is defined as the umber of gram equivalents dissolved per liter of the solution.
Mathematically,
Or,
......(1)
We are given:
Given mass of NaOH = ?
Equivalent mass of NaOH = 40 g/eq
Volume of solution = 400 mL
Normality of solution = 5 eq/L
Putting values in equation 1, we get:
Hence, the mass of solid NaOH required is 80 g
Answer:
evaporation?
Explanation:
evaporate the water leaving behind the sand?
