Explanation:
A physical change is one that alters the physical properties of matter (particularly the form and state).
A chemical change is one in which new kind of matter is formed. It is always accompanied by energy changes (evolution or absorption of energy in form of heat or light or both).
Now, the salient differences between physical and chemical changes;
- Physical changes are easily reversible whereas chemical changes are not easily reversible.
- Physical changes lead to the production of no new kinds of matter whereas chemical changes leads to the production of new kinds of matter.
- Physical changes involves no change in mass whereas chemical changes involves change in mass.
- Physical changes require little energy whereas considerable amount of energy is needed for chemical changes.
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:
1.0 M
Explanation:
Reaction equation;
KOH(aq) + HCl(aq) -----> KCl(aq) + H2O(l)
Concentration of acid CA = ?
Concentration of base CB = 1.0 M
Volume of base VB = 25.60 - 0.50 = 25.1 ml
Volume of acid VB = 25.0 ml
Number of moles of acid NA = 1
Number of moles of base NB =2
CAVA/CBVB =NA/NB
CAVANB = CBVBNA
CA = CBVBNA/VANB
CA = 1 * 25.1 * 1/25.0 *1
CA = 1.0 M
