<h3><u>Answer;</u></h3>
a) It allows electrons to flow from the anode to the cathode.
<h3><u>Explanation</u>;</h3>
- <em><u>Voltaic cell is an electrochemical cell in which a spontaneous chemical reaction produces the flow of electrons</u></em>.
- Electrons are produced by the oxidation reaction occurring at the anode. Electrons flow through the conducting wire from the anode to the cathode. At the cathode these electrons are used to reduce copper(II) ions to copper atoms.
- <em><u>A conducting wire or a wire play connects the two electrodes allowing electrons to flow from the anode to the cathode</u></em>.
Answer:

Explanation:
The contact between the sheet of gold and the sheet of iron allows a heat transfer until thermal equilibrium is done, which means that both sheets have the same temperature:






The final temperature is:

Answer:
Group 18th
Explanation:
The group 18th of periodic table which is composed of Noble gases mainly was missing from the Mendeleev's periodic table. The reason for this is that Noble gases are least reactive, therefore, it was difficult to predict such elements which do not react with other elements.
The volume is 100mL.
The mass is 1.5kg which is equal to 1500g.
Thus, the density is 1500g / 100mL which is 15g/mL.