Which of the following substances is used in black and white photography?

1 Sodium Chloride

 

2. Calcium Hydroxide

 

3. Calcium Nitrate

 

4. Silver Bromide

 

5. None of the above/More than one of the above.

1.

Which of the following aqueous solutions are good buffer systems?
.

0.36 M potassium iodide + 0.23 M potassium bromide

0.29 M ammonia + 0.35 M ammonium bromide

0.15 M acetic acid + 0.11 M sodium acetate

0.18 M sodium hydroxide + 0.25 M sodium chloride

0.28 M hydroiodic acid + 0.22 M potassium iodide

2.

Which of the following aqueous solutions are good buffer systems?
.

0.14 M acetic acid + 0.15 M sodium acetate

0.28 M ammonia + 0.30 M calcium hydroxide

0.18 M barium hydroxide + 0.29 M barium chloride

0.30 M calcium bromide + 0.28 M potassium bromide

0.24 M nitric acid + 0.21 M potassium nitrate

can someone help me understand the first three with steps and the charges? I don't understand why at the end aliuminum problems is 2albr3 +3cl2 yield 2alcl3 3brw?? and help me out with the other problems please.