You can look on the periodic table for the number of automic mass units in each element.
1 mole Li = 6.94 amu
6.94 • 2 = 13.9 amu
There are 13.9 amu in 2 moles of Li
<span>If there are 15 mL in 1 tablespoon, then 3 tablespoons should have triple the volume as originally stated.
Note in all of the four choices, the units simplify to mL because tbsp x ml/tbsp = mL (tbsp/tbsp = 1)
The second and third choice give ultimately the same, incorrect value. The fourth option gives an incorrect fraction - there are not 15 mL for every tablespoon. The correct answer is 1 tbsp x 15mL/3tbsp</span>
Answer:
D. Ni²⁺
Explanation:
We know at once that the answer cannot be A or C, because Ni and Cu are already in their lowest oxidation states.
The correct answer must be either B or D.
An electrolytic cell is the opposite of a galvanic cell. In the former, the reaction proceeds spontaneously. In the latter, you must force the reaction to occur.
One strategy to solve this problem is:
- Look up the standard reduction potentials for the half reaction·
- Figure out the spontaneous direction.
- Write the equation in the reverse direction.
1. Standard reduction potentials
E°/V
Cu²⁺ + 2e⁻ ⟶ Cu; 0.3419
Ni²⁺ + 2e⁻ ⟶ Ni; -0.257
2. Galvanic Cell
We reverse the direction of the more negative half cell and add.
<u>E°/V
</u>
Ni ⟶ Ni²⁺ + 2e⁻; 0.257
<u>Cu²⁺ + 2e⁻ ⟶ Cu; </u> 0.3419
Ni + Cu²⁺ ⟶ Cu + Ni²⁺; 0.599
This is the spontaneous direction.
Cu²⁺ is reduced to Cu.
3. Electrochemical cell
<u>E°/V</u>
Ni²⁺ + 2e⁻ ⟶ Ni; -0.257
<u>Cu ⟶ Cu²⁺ + 2e⁻; </u> <u>-0.3419</u>
Cu + Ni²⁺ ⟶ Ni + Cu²⁺; -0.599
This is the non-spontaneous direction.
Ni²⁺ is reduced to Ni in the electrolytic cell.
Answer:
Chemical change :has change in mass, heat is needed, new element is formed, hard to reverse.......
Physicalchange:does not have change in mass, heat is not necessary, no new element is formed, easy to reverse
CH3COONa+HBr ----> NaBr + CH3COOH
CH3COO⁻ +H⁺ ------> CH3COOH , because CH3COOH is a weak acid
