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sammy [17]
4 years ago
7

If a sample of a substance contains 9.03 x 1023 representative particles, how many moles does this represent?

Chemistry
1 answer:
GaryK [48]4 years ago
5 0
I believe its 10^23 u r saying
then no. of moles= 9.03*10^23/6.02*10^23=1.5mole
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Calculate the ph after 0.020 mol hcl is added to 1.00 l of each of the four solutions below.
melisa1 [442]
A) according to this reaction:
by using ICE table:
              NH2OH(aq) + H2O(l) → HONH3+(aq)   + OH-
initial       0.4 M                                       0                    0
change     -X                                          +X                  +X
Equ        (0.4-X)                                         X                    X

when Kb = [OH-][HONH3+]/[NH2OH]  
when we have Kb = 1.1x10^-8 so,
by substitution:
1.1x10^-8 = X^2/(0.4-X) by solving this equation for X 

∴X = 6.6x10^-5 M
∴[OH] = 6.6x10^-5 M 
when POH = - ㏒[OH]
    ∴POH = -㏒(6.6x10^-5)= 4.18
∴PH = 14 - POH = 14 - 4.18
        = 9.82
when PH = -㏒[H+]
∴[H+] = 10^9.82 = 1.5x10^-10 M+0.02molHcl
          = 0.02
∴ the new value of PH = -㏒(0.02)
∴PH = 1.7

B) according to this reaction:
 by using ICE table:
             HONH3+(aq) → H+(aq) + HONH2(aq)
intial     0.4                          0            0
change -X                          +X           +X
Equ       (0.4-X)                    X              X

when Ka HONH3Cl = 9.09x10^-7 
and Ka = [H+][HONH2] / [HONH3+]

So by substitution and we can assume [HONH3+] = 0.4 as the value of Ka is so small so,
9.09x10^-7 = X^2 / 0.4 by solving for X
∴  X = 6 x 10 ^-4
∴[H+] = 6x10^-4
PH = -㏒[H+] 
      = -㏒ (6x10^-4) = 3.22
when [H+] = 6x10^-4 + 0.02 m HCl 
∴new value of PH = -㏒(6x10^-4+0.02)
                               = 1.69
C) when we have pure H2O and PH of water = 7
So we can get [H+] when PH = -㏒[H+]
∴[H+] = 10^-7 + 0.02MHCl
          = 0.02
∴new value of PH = -㏒0.02
                         PH = 1.7
d) when HONH2 & HONH3Cl have the same concentration and Hcl added to them so we can assume that PH=Pka
and when we have Ka for HONH3Cl = 9.09x10^-7 
So we can get the Pka:

Pka = -㏒Ka
       = -㏒9.09x10^-7
       = 6.04
∴PH = 6.04
and because of the concentration of the buffer components, HONH2 & HONH3Cl have 0.4 M and the adding of HCl = 0.02 M So PH will remain very near to 6 






4 0
3 years ago
4.702 x 10^-4 in standard form?
Julli [10]
The answer is .0004704. i hope that helped.
7 0
3 years ago
How much heat is required to raise the<br> temperature of 835g of water from 35.0°C to<br> 65.0°C?
Anna007 [38]

Answer:

25,050 calories.

Explanation:

A calorie is the amount of energy needed to raise the temperature of one gram of water 1 degree centigrade. If we are raising 835 grams of water 30 degrees then we multiply 835*30 to get 25,050 calories.

3 0
3 years ago
What is the volume in liters of 321 g of liquid with a density of 0.84 g/mL
Rasek [7]
Density is weight by volume.   

First.  If you divide the weight by density you can find the volume

Second you must convert the ML in to Liters.

\frac{321 \frac{g}{1}}{0.84 \frac{g}{mL}} = \frac{321(g)(mL)}{0.84g}=\frac{321mL}{0.84}=382.14mL

1L=1000ml

\frac{1L}{1000mL}

(382.14mL)( \frac{1L}{1000mL})= \frac{(382.14mL)(L)}{1000mL} =\frac{382.14L}{1000}=0.38214L

0.38214 Liters.

4 0
4 years ago
Help only 4 minutes left
vesna_86 [32]

Answer: the answer is d

Explanation: hurry and answer

4 0
3 years ago
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