Answer:
CuSO4
Explanation:
Na2S + CuSO4 → Na2SO4 + CuS
The reaction is balanced (same number of elements in each side)
To determine limiting reagent you need to know the moles you have of each.
Molar mass Na2S = 23 * 2 + 32 = 78
Molar mass CuSO4 = 63.5 + 32 + 16 * 4 = 159.5
Na2S mole = 15.5 / 78 = 0.2
CuSO4 mole = 12.1/159.5 = 0.076
*Remember mole = mass / MM
With that information now you have to divide each moles by its respective stoichiometric coefficient
Na2S stoichiometric coefficient : 1
Na2S : 0.2 / 1 = 0.2
CuSO4 stoichiometric coefficient: 1
CuSO4: 0.076 / 1 = 0.076
The smaller number between them its the limiting reagent, CuSO4
Answer is: B because it has a lower activation energy.
For all chemical reaction some energy is required and that energy is called activation energy (energy that needs to be absorbed for a chemical reaction to start), activation energy for reaction B is lower that for reaction A.
Catalysis is the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalyst.
Chemical reactions occur faster with a catalyst because they require less activation energy.
No, the water is not different it is just that the units of measurement in the US is different then those units in Europe. This is similar to how the US uses miles and Europe uses kilometers
Answer:

Explanation:
Here, we wnat to get the most electronegative atom
On the periodic table, electronegativity increases across a period and decrease down the group
The elements listed are in the same group
Boron is the first member of the group
Boron is the most electronegative atom in the group