Answer:
Complex formation
Explanation:
At first sight, one may think that a reaction between calcium oxalate and platinum metal is impossible considering the relative positions of the two metals in the electrochemical series.
However, in solution, calcium oxalate dissociates into calcium and oxalate ions. When platinum is added to this solution, a complex is formed between the platinum ions and the oxalate ions. Hence a reaction occurs for this reason.
Answer:
La densidad experimenta una disminución
Explanation:
Hola!
En este caso, debemos recordar que la adición de agua incrementa el volumen donde se encuentra un soluto disuelto, el cual posee una cantidad de materia constante. De este modo, sabiendo que la densidad es:

Al incrementar el denominador (volumen), la densidad experimenta una disminución, al estar en relación inversamente proporcional.
Muchos saludos!
Endothermic reaction is the answer.
Answer:
I think that is the literal answer