PLZ HELP CHEMISTRY! WILL REWARD! Please correct me if I'm wrong. I marked my answers as x.

1. During a titration, 50.0 ml of 0.2M NaOH were required to neutralize 50.0ml of H3PO4. What's the concentration of the H3PO4 solution?

A. 1.8M
B. 0.6M
C. 0.07M
x D. 0.2M

2. Attached photo - Using the two cell reduction potentials shown for their corresponding reaction, calculate the cell potential for a voltaic cell made from these two systems.

A. –1.68 V
B. –0.78 V
C. 0.78 V
D. 1.68 V

3. If atoms from two different elements react to form a compound, the element with a higher _ will have a negative oxidation number.

A. atomic number
B. atomic radius
C. energy
x D. electronegativity

4. During the electrolysis of an aqueous solution of sodium nitrate, a gas forms at the anode, what gas is it?

x A. Oxygen
B. Hydrogen
C. Sodium
D. Water

5. The lithium-ion in a lithium-ion battery moves from one side to the other by

A. moving through the cathode.
B. moving through the anode.
x C. passing through the separator.
D. passing through the device.

6. The use of water in a heat exchanger is taking advantage of water's

x A. high specific heat.
B. significant expansion during boiling.
C. solid state when frozen.
D. polar molecular nature.

Which of the following goes through the largest volumetric change?

A. Water when it boils into steam
x B. Water when it freezes into ice
C. Water when it's heated from 1oC to 99oC
D. Ice when it melts into water

Explanation:

1. During a titration, 50.0 ml of 0.2M NaOH were required to neutralize 50.0ml of H3PO4. What's the concentration of the H3PO4 solution?

Using CaVa / CbVb = Na / Nb. The correct option is D.

3. If atoms from two different elements react to form a compound, the element with a higher will have a negative oxidation number.

The correct option is electronegativity. For example, in H2O. Oxygen would have a negative oxidation number of -2 because it is highly electronegative compared to hydrogen. Also, a negative oxidation number means it gains electrons.

4. During the electrolysis of an aqueous solution of sodium nitrate, a gas forms at the anode, what gas is it?

At the anode, OH- ions are preferentially discharged. They lose electrons there and form oxygen gas. The correct option is A. Oxygen

5. The lithium-ion in a lithium-ion battery moves from one side to the other by

The correct option is passing through the separator. The lithium ions, moves from the anode to the cathode when in use.

6. The use of water in a heat exchanger is taking advantage of water's

The correct option is it's High specific heat capacity. Since heat exchangers requires transfer of heat, there is need for a medium that is able to carry this heat. The hydrogen bonds in water provides it with an abnormal high specific heat capacity.

7. Which of the following goes through the largest volumetric change?

Whenever ice melts it occupies the same energy as when it was frozen. When water is heated from 1oC to 99oC there is no change in volume. Volume of water increases abruptly at it boils at 100oC  and changes its state from liquid water to steam. When water freezes it's volume increases by approximately 9%. The correct option is A.

Kindly Note:

Next time, You don't have to ask everything in a single question. Nobody would want to go through the stress of answering them all. I omitted number 2 intentionally.