Answer:
b. Heat flows from the surroundings to the system and the temperature of the water decreases.
Explanation:
The laws of thermodynamics lets us know that energy is neither created nor destroyed but can be converted from one form to another. Also, energy transfer does accompany chemical reactions in the form of heat.
For an endothermic reaction, heat is absorbed by the system from the surroundings. This leads to a drop in the temperature of the surroundings as energy is removed.
This implies that the water temperature decreases.
<h3>1</h3>
Species shown in bold are precipitates.
- Ca(NO₃)₂ + 2 KOH → Ca(OH)₂ + 2 KNO₃
- Ca(NO₃)₂ + Na₂C₂O₄ → CaC₂O₄ + 2 NaNO₃
- Cu(NO₃)₂ + 2 KI → CuI₂ + 2 KI
- Cu(NO₃)₂ + 2 KOH → Cu(OH)₂ + 2 KNO₃
- Cu(NO₃)₂ + Na₂C₂O₄ → CuC₂O₄ + 2 NaNO₃
- Ni(NO₃)₂ + 2 KOH → Ni(OH)₂ + 2 KNO₃
- Ni(NO₃)₂ + Na₂C₂O₄ → NiC₂O₄ + 2 NaNO₃
- Zn(NO₃)₂ + 2 KOH → Zn(OH)₂ + 2 KNO₃
- Zn(NO₃)₂ + Na₂C₂O₄ → ZnC₂O₄ + 2 NaNO₃
<h3>2</h3>
A double replacement reaction takes place only if it reduces in the concentration of ions in the solution. For example, the reaction between Ca(NO₃)₂ and KOH produces Ca(OH)₂. Ca(OH)₂ barely dissolves. The reaction has removed Ca²⁺ and OH⁻ ions from the solution.
Some of the reactions lead to neither precipitates nor gases. They will not take place since they are not energetically favored.
<h3>3</h3>
Compare the first and last row:
Both Ca(NO₃)₂ and Zn(NO₃)₂ react with KOH. However, between the two precipitates formed, Ca(OH)₂ is more soluble than Zn(OH)₂.
As a result, add the same amount of KOH to two Ca(NO₃)₂ and Zn(NO₃)₂ of equal concentration. The solution that end up with more precipitate shall belong to Zn(NO₃)₂.
<h3>4</h3>
Compare the second and third row:
Cu(NO₃)₂ reacts with KI, but Ni(NO₃)₂ does not. Thus, add equal amount of KI to the two unknowns. The solution that forms precipitate shall belong to Cu(NO₃)₂.
The answer is yes. A chemical change occurred.
Chemical change is defined as the rearrangement or alteration in the of atoms in one or more substance which result in the formation of a new substance.
In the above, you mixed two clear liquids and the result was a new substance which is a colored solid precipitate at the bottom of the beaker.
This means that changes in the atoms of the two clear liquids occurred leading to the formation of this new solid substance.
This means that chemical change has occurred.
Hope this helps :)
napthalene: C10H8 sulphur: S02
Explanation:
C10H8
