Answer:
May be the instrument is incorrect or may be error in it.
Explanation:
The copper have not been detected by this test because the test may be not for the detection of copper, may be it is used for identification of another minerals. If there is copper in the lake sample but can't be detected in the test so it means that the instrument which is used for detection is not the right one or having error in that instrument. Every mineral has a specific type of instrument that detect its presence, if we use incorrect instrument for the mineral then we can't detect the presence of that specific mineral.
Answer: its a single replacement reaction
I'm happy to help but do you have the options?
Answer:
Si.
Explicación:
Sí, el método de cristalización se utiliza para separar la sal del agua y obtener los componentes de la sal y del agua por separado. La cristalización es un método o técnica que se utiliza para purificar compuestos sólidos. Este proceso funciona mejor debido a las diferentes solubilidades del compuesto deseado y las impurezas que están presentes en un solvente dado. El proceso de cristalización implica enfriar agua salada para formar cristales de hielo puro. Luego, los cristales de hielo se separan de la salmuera no congelada, se lavan para eliminar la sal residual y luego se derrite la solución para producir agua dulce.
Explanation:
The reaction equation will be as follows.
Using bond energies, expression for calculating the value of 
is as follows.
On reactant side, from 
number of bonds are as follows.
C-C bonds = 1
C-H bonds = 6
From 
; Cl-Cl bonds = 1
On product side, from 
number of bonds are as follows.
C-C bonds = 1
C-H bonds = 5
C-Cl bonds = 1
From HCl; H-Cl bonds = 1
Hence, using the bond energies we will calculate the enthalpy of reaction as follows.
=![[(1 \times 348 kJ/mol) + (6 \times 414 kJ/mol) + (1 \times 242 kJ/mol)] - [(1 \times 348 kJ/mol) + (5 \times 414 kJ/mol) + (1 \times 327 kJ/mol) + (1 \times 431 kJ/mol)]](https://tex.z-dn.net/?f=%5B%281%20%5Ctimes%20348%20kJ%2Fmol%29%20%2B%20%286%20%5Ctimes%20414%20kJ%2Fmol%29%20%2B%20%281%20%5Ctimes%20242%20kJ%2Fmol%29%5D%20-%20%5B%281%20%5Ctimes%20348%20kJ%2Fmol%29%20%2B%20%285%20%5Ctimes%20414%20kJ%2Fmol%29%20%2B%20%281%20%5Ctimes%20327%20kJ%2Fmol%29%20%2B%20%281%20%5Ctimes%20431%20kJ%2Fmol%29%5D)
= -102 kJ/mol
Thus, we can conclude that change in enthalpy for the given reaction is -102 kJ/mol.
