Answer:
When the solution (with phenolphthalein) changes to colorless
Explanation:
When titrating with HCl is common to add phenolphthalein as an acid-base indicator.
Phenolphthalein is pink or fucsia when added into a basic solution. On the other hand when it is in acid solutions, is colorless.
So, when titrating, the NaOH solution will be initialy pink due to the phenolphthalein and when reaching the equivalence point, that color will fade out into colorless. This is how you know you hace reached the equivalent point.
A formula unit is the same as the empirical formula of a compound or an ionic molecule. It is the lowest ratio of the atoms in the compound or ion. Zinc acetate ions dissociates into zinc ions and acetate ions. The dissociation reaction is expressed as follows:
Zn(O2CCH3)2 = Zn2+ + 2(O2CCH3)1-
We determine the amount of acetate ions produced as follows:
Moles Zn(O2CCH3)2 = (3 formula units Zn(O2CCH3)2) ( 1 mol / 6.022x10^23 formula units) = 4.98x10^-24 mol Zn(O2CCH3)2
moles (O2CCH3)1- = 4.98x10^-24 mol Zn(O2CCH3)2 ( 2 mol (O2CCH3)1- / 1 mol Zn(O2CCH3)2 ) = 9.96x10^-24 mol (O2CCH3)1-
# of acetate ions = 9.96x10^-24 mol (O2CCH3)1- ( 6.022x10^23 ions / 1 mol (O2CCH3)1-) = 6 acetate ions
Answer:
P.E = 25.48 J
Explanation:
Given data:
Mass = 2 Kg
Height = 1.3 m
Potential energy = ?
Solution:
Formula:
P.E = m . g . h
P. E = potential energy
m = mass in kilogram
g = acceleration due to gravity
h = height
Now we will put the values in formula.
P.E = m . g . h
P.E = 2 Kg . 9.8 m /s² . 1.3 m
P.E = 25.48 Kg. m² / s²
Kg. m² / s² = J
P.E = 25.48 J
Answer:
This experiment is uncontrolled because two different masses of substance A are used.
Explanation:
A controlled experiment is a structured experiment aimed at testing a particular observation or observations. The setup of a controlled experiment helps to determine the reason why a particular observation occurs and what must have led to it.
In the experiment highlighted above, different masses of a substance were used, they were heated to different temperatures. The set up does not show any correlation between the masses of substances heated and the temperatures. It is even difficult to try to predict the hypothesis for this kind of experimental set up. All the variables in play can best be assumed to be independent of one another.
