The answer is: II.The endpoint is recorded when the solution is dark red in color rather than light pink.
The endpoint is the point at which the indicator changes colour in a colourimetric titration and that is point when titration must stop.
Phenolphthalein is colorless in acidic solutions and pink in basic solutions. If this indicator change color to dark red, more base is added and endpoint is not accurate.
If the the acid is spilled before titration, that does not make endpoint wrong and molar mass can be calculated.
In this example we can take acetic acid as carboxylic acid; basic salt sodium acetate CH₃COONa is formed from the reaction between weak acid (in this example acetic acid CH₃COOH) and strong base (in this example sodium acetate NaOH).
Balanced chemical reaction of acetic acid and sodium hydroxide:
CH₃COOH(aq) + NaOH(aq) → CH₃COONa(aq) + H₂O(l).
Neutralization is is reaction in which an acid (in this example vinegar or acetic acid CH₃COOH) and a base react quantitatively with each other.
They are called isotopes.
Isotopes have the same number of electrons and protons in their unionized state. They differ in the number of neutrons. The first and simplest example is hydrogen.
The most common hydrogen has
1 proton
1 electron and
0 neutrons
It has 2 cousins
1 proton
1 electron
1 neutron
And
1 proton
1 electron
2 neutrons.
Most elements have some differences in the number of neutrons present in their nuclei. Cesium and Xenon have the most number of isotopes. Each has 36. You wonder how the atoms are held together.
Answer: The density of 0.50 grams of gaseous carbon stored under 1.50 atm of pressure at a temperature of -20.0 °C is 0.867 g/L.
Explanation:
- d = m/V, where d is the density, m is the mass and V is the volume.
- We have the mass m = 0.50 g, so we must get the volume V.
- To get the volume of a gas, we apply the general gas law PV = nRT
P is the pressure in atm (P = 1.5 atm)
V is the volume in L (V = ??? L)
n is the number of moles in mole, n = m/Atomic mass, n = 0.50/12.0 = 0.416 mole.
R is the general gas constant (R = 0.082 L.atm/mol.K).
T is the temperature in K (T(K) = T(°C) + 273 = -20.0 + 273 = 253 K).
- Then, V = nRT/P = (0.416 mol)(0.082 L.atm/mol.K)(253 K) / (1.5 atm) = 0.576 L.
- Now, we can obtain the density; d = m/V = (0.50 g) / (0.576 L) = 0.867 g/L.
