How do I perform a titration on coca-cola or Pepsi, when I cannot see the color change because the color is too dark. The indicator is phenolphthalein.

maybe you need to do very dilute solution?

Explanation: you should have an pH meter instead of indicator.

Phosphoric acid H3PO4 have three ekvivalent points.

Another way could be using a conductivity meter.

HBr has the lowest rate of effusion at a given temperature.

Explanation: The effusion rate usually increases with increase in temperature because the kinetic energy of the gaseous molecules increases. But it was not true for gases having heavier mass. This was explained by Graham's Law.

Graham's Law states that the rate of effusion of a gas is inversely proportional to the square root of its molecular weight.

We are given different gases with different Molecular masses. The gas having larger Molecular mass will have the lowest rate of effusion.

Mol. Mass of = 80 g/mol

Mol. Mass of = 16 g/mol

Mol. Mass of = 17 g/mol

Mol. Mass of HBr = 81 g/mol

Mol. Mass of HCl = 36 g/mol

As, Mol. mass of HBr is the highest, so its rate of effusion will be the lowest.