Mass of MnO2 = 25 g
The reaction would be 3MnO2 + 4Al --> 3Mn(s) + 2Al2O3
Molar mass of Al = 26.982 g/mol
Molar mass of MnO2 = 54.938 + 2(15.999) = 86.936 g/mol
Calculating the moles = 25 / 86.936 = 0.2876 mol.
Mole ratio MnO2 and Al considering the equation = 3 mol of MnO : 4 mol of Al
Calculating the moles of Al = 0.2876 mol MnO2 x (4 mol of Al / 3 mol of MnO)
Number of moles of Al = 0.3834
Getting the mass in grams as asked = 0.3834 mol x 26.982 g/mol = 10.34 grams.
pH=6.98
Explanation:
This is a very interesting question because it tests your understanding of what it means to have a dynamic equilibrium going on in solution.
As you know, pure water undergoes self-ionization to form hydronium ions, H3O+, and hydroxide anions, OH−.
2H2O(l]⇌H3O+(aq]+OH−(aq]→ very important!
At room temperature, the value of water's ionization constant, KW, is equal to 10−14. This means that you have
KW=[H3O+]⋅[OH−]=10−14
Since the concentrations of hydronium and hydroxide ions are equal for pure water, you will have
[H3O+]=√10−14=10−7M
The pH of pure water will thus be
pH=−log([H3O+])
pH=−log(10−7)=7
Now, let's assume that you're working with a 1.0-L solution of pure water and you add some 10
D. All of the above. Developing medicine, analyzing compounds and producing new product such as plastic all have to deal with chemistry.
We all struggle in some subjects, you do badly when you don't try, and sometimes we try and can't get the answer, I'll help with that. :)
The first answer is CO2(g), CO2 is a gas, and all gas have... 4) No definite shape, no definite volume.
A piece of ice, a block of wood, and a ceramic cup are solids. They have shapes that do not change and volumes that can be measured. Any matter that is a solid has a definite shape and a definite volume.
A liquid takes the shape of what holds it, besides a flat surface, which will just evidently, take the shape of a flat surface. A liquid has a definite volume, because the volume of a liquid is constant because forces of attraction keep the particles loosely together.
Gases attempt to fill a container of any shape or size. Therefore, it has no definite shape.
There are forces of attraction among the particles in all matter, therefore, it has no definite volume.
The second question might become easier with the explanation above. A liquid has a definite volume because the forces of attraction are loosely together! Therefore, it has a definite volume, but it will take the shape of it's container.
This means... Yes! 2) It retains its original volume but changes shape.
This one is easy. To convert one gram of a solid at its normal heating point to a liquid at the same temperature, is the 1) Heat of Vaporization.
Heat of Vaporization is the amount of heat energy required to convert one gram of a substance from a liquid to a gas.
The third question, the molecules for H20, in a solid phase are always in an geometric and arranged pattern.
Most solids are arranged in geometric and arranged patterns, and since H20 is not in its indefinitely shaped liquid phase, it has a definite shape and thus, retains a repeating (geometric) pattern.
(Note- Some solids like wax or rubber do not have an arranged or geometric pattern.)
The “average of a kinetic energy” is defined as the vitality of movement of particles of a framework.
Or in simpler terms, “energy motion”.
So when temperature increases, the average kinetic energy of a molecule(s) 1) increases.
Answer:
pKa = 3.675
Explanation:
∴ <em>C</em> X-281 = 0.079 M
∴ pH = 2.40
let X-281 a weak acid ( HA ):
∴ HA ↔ H+ + A-
⇒ Ka = [H+] * [A-] / [HA]
mass balance:
⇒<em> C</em> HA = 0.079 M = [HA] + [A-]
⇒ [HA] = 0.079 - [A-]
charge balance:
⇒ [H+] = [A-] + [OH-]... [OH-] is negligible; it comes from to water
⇒ [H+] = [A-]
∴ pH = - log [H+] = 2.40
⇒ [H+] = 3.981 E-3 M
replacing in Ka:
⇒ Ka = [H+]² / ( 0.079 - [H+] )
⇒ Ka = ( 3.981 E-3 )² / ( 0.079 - 3.981 E-3 )
⇒ Ka = 2.113 E-4
⇒ pKa = - Log ( 2.113 E-4 )
⇒ pKa = 3.675
