At the point when a response achieves a condition of concoction balance under a specific arrangement of conditions, no further changes in the groupings of reactants and items happen. On the off chance that a change is made in the conditions under which the framework is at harmony, substance change will happen so as to build up another balance. The components that can impact harmony are an adjustment in focus, change in weight (or volume), and change in temperature.
Answer is: because pH value of solution is changing.
Balanced chemical reaction: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l).
pH of sodium hydroxide solution is above seven (basic), when solution of hydrochloric acid is added, pH slowly dropping until it became neutral solution (pH is equal seven) and that is endpoint of titration.
Surface tension is defined as the tendency of elasticity of a liquid surface that makes it to achieve the possible least surface area. It depends upon the intermolecular forces present on the boundary of the surface of the compound and its contact.
n-butane 
is non-polar compound and it consist of only weak dispersion forces that are responsible for any contact with the surface.
In comparison to other given substances, n-butane has the weakest dispersion forces. Thus, n-butane has lowest surface tension.
0.000345 in scientific notation is 3.45*10^-4
Answer:
The mass number of an element is the sum of protons and neutrons.
Hence, 53+66 =119
The mass number of the atom is 119.
