Answer:
1.58x10⁻⁵
2.51x10⁻⁸
0.0126
63.10
Explanation:
Phenolphthalein acts like a weak acid, so in aqueous solution, it has an acid form HIn, and the conjugate base In-, and the pH of it can be calculated by the Handerson-Halsebach equation:
pH = pKa + log[In-]/[HIn]
pKa = -logKa, and Ka is the equilibrium constant of the dissociation of the acid. [X] is the concentrantion of X. Thus,
i) pH = 4.9
4.9 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = - 4.8
[In-]/[HIn] = 
[In-]/[HIn] = 1.58x10⁻⁵
ii) pH = 2.1
2.1 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = -7.6
[In-]/[HIn] = 
[In-]/[HIn] = 2.51x10⁻⁸
iii) pH = 7.8
7.8 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = -1.9
[In-]/[HIn] = 
[In-]/[HIn] = 0.0126
iv) pH = 11.5
11.5 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = 1.8
[In-]/[HIn] = 
[In-]/[HIn] = 63.10
Answer:
2.8x10^24
Explanation:
To convert moles to molecules, multiply the number of moles by Avagadro's number (6.02x10^23. Round if required.
4.62mol × 6.02x10^23 = 2.8x10^24
Convection currents in the Earth's mantle cause plate movement which causes earthquakes and volcanic activity.
Answer:
5.90, 11.8, 47.2
Explanation:
Let’s remove the parentheses and write the formula as MgCl₂O₈.
We see that 1 mol Mg(ClO₄)₂ contains 1 mol Mg atoms, 2 mol Cl atoms, and 8 mol O atoms.
∴


∴ Mg, Cl, O = 5.90, 11.8, 47.2
Answer:
Explanation:
The mass of an atom is dependent on its number of protons and neutrons. Electrons have mass, but are too light in comparison to protons and neutrons to contribute towards the overall mass. Their relative mass is about 1/1840 compared to 1 for protons and neutrons, and therefore are not counted in the mass.
Hope this helped!