What is the reagent used and appropriate temperature required to prepare ethene from ethyl alcohol?

Q. Which of the following is used to prepare ${Cl}_2$ gas at room temperature from concentrated $HCl$?

Q.

A, B, C and D summarize the properties of sulphuric acid depending on whether it is dilute or concentrated. Choose the property (A, B, C or D), depending on which is relevant to each of the preparations (i) to (iii):
A. Dilute acid (typical acid properties)
B. Non-volatile acid
C. Oxidizing agent
D. Dehydrating agent
(i) Preparation of hydrogen chloride.
(ii) Preparation of ethene from ethanol.
(iii) Preparation of copper sulphate from copper oxide.

Q. What volume of 12.5 M concentrated HCl is required to make 1 L of 0.1 M HCl solution?

Q. When ethanol is heated with excess of concentrated sulphuric acid at $170{}^o\text{C}$, it gets converted to ethene. In this reaction, concentrated sulphuric acid acts as:

Q. How is phosphine prepared using the following reagents?
(a) $HCl$
(b) $H_{2}S{O}_4$
(c) Caustic soda