Answer :
The concentration of 
before any titrant added to our starting material is 0.200 M.
The pH based on this ion concentration is 0.698
Explanation :
First we have to calculate the concentration of before any titrant is added to our starting material.
As we are given:
Concentration of HBr = 0.200 M
As we know that the HBr is a strong acid that dissociates complete to give hydrogen ion and bromide ion 
.
As, 1 M of HBr dissociates to give 1 M of
So, 0.200 M of HBr dissociates to give 0.200 M of
Thus, the concentration of before any titrant added to our starting material is 0.200 M.
Now we have to calculate the pH based on this ion concentration.
pH : It is defined as the negative logarithm of hydrogen ion concentration.
![pH=-\log [H^+]](https://tex.z-dn.net/?f=pH%3D-%5Clog%20%5BH%5E%2B%5D)
Thus, the pH based on this ion concentration is 0.698
Answer: The correct sequence for the series of event would be.
1. Igor's toe is being cut by the glass.
2. The wound surrounding the injury becomes infected with bacteria from Igor's foot.
3. Antibodies and circulating white blood cells stick to the bacteria creating a large complex in the lymph vessel.
4. The bacteria enter his lymph system and travel towards a lymph node.
5. The complex becomes trapped in a lymph node and is engulfed by a phagocyte.
6. The bacteria is destroyed.
Explanation:
Whenever there is any cut or wound in the body and body encounters invasion of the foreign materials it considers it as harmful pathogen.
These pathogens when enters the body it is considered as antigen, it then travels to the lymphatic system.
These bacterial complex is then killed by the phagocytes and digested by the body.
In this way the complex is killed and the bacteria is destroyed.
Answer : The correct option is, 0.21 moles
Solution : Given,
Molarity of the solution = 0.85 M = 0.85 mole/L
Volume of solution = 250 ml = 0.25 L 
Molarity : It is defined as the number of moles of solute present in one liter of the solution.
Formula used :
Now put all the given values in this formula, we get the moles of solute of the solution.
Therefore, the moles of solute is, 0.21 moles
The answer is homogenous i think
