A solid sample of Zn(OH)2 is added to 0.400 L of 0.550 M solution of HBr. The solution that remains is still acidic. It is then titrated with 0.500 M NaOH solution, requiring 165 mL of the NaOH solution to react completely. What mass of Zn(OH)2 was added to the HBr solution

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?