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Levart [38]
3 years ago
11

We might think of a porous material as being a composite wherein one of the phases is a pore phase. Estimate upper and lower lim

its for the room-temperature thermal conductivity of a magnesium oxide material having a volume fraction of 0.10 of pores that are filled with still air.
Chemistry
1 answer:
eduard3 years ago
8 0

Answer:

The upper and lower limits for the room-temperature thermal conductivity of a magnesium oxide material having a volume fraction of 0.10 of pores that are filled with still air are

Ku = 38.252 W/mK

K lower = 0.199 W/mK

Explanation:

As we know  

Ku = Vp * Kair + Vmagnesium * K metal  

Ku = 0.10 *0.02 + (1-0.25) * 51

Ku = 38.252 W/mK

The lower limit  

K lower = Kmetal* Kair/( Vp * Kmetal + Vmetal * K air)

K lower = (0.02*51)/(0.10*51 + 0.90 * 0.02)

K lower = 0.199 W/mK

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Calculate the percent dissociation of trimethylacetic acid(C6H5CO2H) in a aqueous solution of the stuff.
Sophie [7]

Answer:

1.112%.

Explanation:

Step one : write out the correct acid dissociation reaction. This is done below:

C6H5CO2H <=====> C6H5CO2^- + H^+.

At equilibrium, the concentration of C6H5CO2H = 0.5 M - x and the concentration of C6H5CO2^- = x and the concentration of H^+ = x.

The ka for C6H5CO2H = 6.3 × 10^-5.

Step two: find the value for the concentration of C6H5CO2^- and H^+. This can be done by using the equilibrium dissociation Constant formula below;

Ka = [C6H5CO2^- ] [H^+] / C6H5CO2H.

ka = [x] [x] / [0.5 - x].

6.3 × 10^-5 = (x)^2 / [0.5 - x].

x^2 = 3.15 ×10^-5 - 6.3 × 10^-5 x.

x^-2 + 6.3 × 10^-5 x - 3.15 × 10^-5.

Solving for x we have x= 0.0055632289702004 = 0.00556.

Therefore, at equilibrium the concentration of H^+ = 0.00556 M and the concentration of C6H5CO2H= O.5 - 0.00556 = 0.494 M.

Step three: Calculate the equilibrium pH. This stage can be ignored for this question since we are not asked to calculate for the pH.

The formular for pH = - log [H^+].

pH= - log [0.00556].

pH= 2.255.

Step four: find the percentage dissociation.

Percentage dissociation = ( [H^+] at equilibrium/ [ C6H5CO2H] at Initial concentration ) × 100%.

Percentage dissociation=( 0.00556/ 0.5 ) × 100.

=Percentage dissociation= 1.112%.

3 0
3 years ago
Consider the reaction between HCl and O2: 4HCl(g)+O2(g)→2H2O(l)+2Cl2(g) When 63.1 g of HCl is allowed to react with 17.2 g of O2
alina1380 [7]

Answer:

The limiting reactant for this reaction is the HCl

Explanation:

This is my reaction:

4HCl(g)+O2(g)→2H2O(l)+2Cl2(g)

Molar mass O2 = 32 g/mol

Molar mass HCl = 36,45 g/mol

Mass / Molar mass = Moles

Moles HCl : 63,1 g / 36,45 g/m = 1,73 moles

Moles O2: 17,2 g / 32g/m =  0,54 moles

4 moles of HCl react with 1 mol of O2, according to reaction, so

1,73 moles of HCl, are going to react with, how many moles of O2.

4 moles HCl ___ 1 mol O2

1,73 moles HCl ___ (1,73 . 1)/ 4 = 0,43 moles of O2

O2 is my excess reagent because I need 0,43 moles and I have 0,54 so I have moles in excess.

1 mol of O2 are going to react with 4 moles of HCl

0,54 moles of O2 are going to react with, how many moles of HCl ?

1 mol O2 ____ 4 moles HCl

0,54 mol O2 ___ (0,54 . 4)/ 1 = 2,16 moles

I need 2,16 moles to consume my moles of O2, but I only have 1,73 moles, tha's why the HCl is mi limiting reactant.

3 0
3 years ago
If you want to lift a 30-kg box to a height of 1 m, how much work will it take?
natta225 [31]

Explanation:

workdone = force x distance

force = mass x acceleration

30 x 10 = 300N

300N x 1m

workdone= 300J

7 0
3 years ago
If the mass of a material is 106 grams and the volume of the material is 23 cm3, what would the density of the material be? g/cm
den301095 [7]
Density is mass over volume
Density = 106g/23cm³ = 4.6g/cm³
7 0
3 years ago
What experiment did Robert Millikan do?
scZoUnD [109]
I’m not sure it’s correct but I think it’s D) He used voltage adjustments to make charges oil drops float
7 0
4 years ago
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