Question

please and please choose the right answer and please make it clear for my understanding

1-Which of the following statements are false?

		Oxidation and reduction half-reactions occur at electrodes in electrochemical cells
		All electrochemical reactions involve the transfer of electrons
		Oxidation occurs at the anode
		All voltaic (galvanic) cells involve the use of electricity to initiate nonspontaneous chemical reactions
		Reduction occurs at the cathode

2-During the electrolysis of aqueous KCl solution using inert electrodes, gaseous hydrogen is evolved at one electrode and gaseous chlorine at the other.

The solution around the electrode at which hydrogen gas is evolved becomes basic as the electrolysis proceeds.

Select the correct statements which describe or are applicable to the cathode and the reaction that occurs there.

		the negative electrode
		electrons flow into the electrode from the external circuit
		electrons flow from the electrode to the external circuit
		reduction
		the positive electrode
		2H2O + 2e- --> H2 + 2OH-
		2Cl- --> Cl2 + 2e-
		Cl2 + 2e- --> 2Cl-
		oxidation
		2H2O --> O2 + 4H+ + 4e-

3-For a voltaic (galvanic) cell using Ag,Ag⁺ and Zn,Zn2+ half-celss, which of the statements are incorrect?

		Reduction occurs at the zinc electrode as the cell operates
		the concentration of Ag+ will decrease as the cell operates
		the zinc electrode is the anode
		electrons flow through the external circuit from the zinc electrode to the silver electrode
		the mass of the zinc electrode decreases as the cell operates

4-Which of the following statements are true for ALL voltaic (galvanic) cells

		the anode gains mass during operation of the cell
		the voltage is less than or equal to zero
		reduction occurs at the cathode

5-In a voltaic cell, the salt bridge:

		allows charge balance to be maintained in the cell
		is tightly passed with firm agar gel through which ions cannot pass
		acts as a mechanism to allow mechanical mixing of the solutions
		is not necessary for the cell to work
		drives free electrons from one half cell to the other

6-For the cell given below, which equation represents the reaction that occurs at the negative electrode?

Pb / Pb(NO₃)₂ || AgNO₃ / Ag

(hint: the strip of silver gains mass)

		Pb2+ + 2e- ---> Pb
		Ag+ + e- --> Ag
		Ag --> Ag+ + e-
		Pb --> Pb2+ + 2e-

7-Calculate the mass of one mole of caffeine in grams. Round your answer to the nearest whole number.

Caffeine: C₈H₁₀N₄O₂

Molar masses (g/mol)

C = 12.011

H = 1.0079

N = 14.007

O = 15.999

8-A recent survey stated that the average American adult ingests 170mg of caffeine per day.

How many molecules is that? (Use unrounded answer from previous question).

9-How many hydrogen atoms are there in 1 litre of water?

(round answer appropriately)

10-Solid object A weighs more than solid object B.

Consequently we can conclude that:

		A's volume must be greater than B's
		both A's density and volume must be greater than B's
		measurements would be required to determine the cause of the weight difference
		A's density must be greater than B's

11-Two aquariums are completely full of water, but hte pressure at the bottom of aquarium A is greater than that at the bottom of aquarium B.

The cause of this could be:

		A contains freshwater and B contains seawater
		the water in A is deeper than it is in B
		A is shaped like a box and B is shaped like a cylinder
		Any of the above