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3 years ago

Calculate the molar solubility of lead thiocyanate in 1.00 M KSCN.

1 answer:

7 0

You have to make an assumption or estimation here: (don't think about the 1.00 M KSCN)
Since 1.00M KSCN provides a common ion source of SCN-. Therefore, you will have a 1.00 M SCN-.
[Pb+2][SCN-] ~ 0.01 x 0.02^2 = 4E-6
 Pb(SCN)2 <---> Pb++ + 2SCN- 

Bringing 1.00M SCN- back in the problem. 1.00M + 0.02M, ignoring the SCN-, and calculating the [Pb+2]:

Ksp = [Pb++][SCN-]^2
2.00E-5 = [Pb++](1.00)^2

[Pb++] = 2.00E-5 M 

The mass balance shows that: 

[Pb++] = [Pb(SCN)2] 

So [Pb(SCN)2] = 2.00E-5 M in 1.00 M KSCN.

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1) How many molecules are there in 985 mL of nitrogen at 0.0° C and 1.00 x 10-6 mm Hg?

RSB [31]

Answer : The number of molecules present in nitrogen gas are, $3.48\times 10^{13}$

Explanation :

First we have to calculate the moles of nitrogen gas by using ideal gas equation.

$PV=nRT$

where,

P = Pressure of $N_2$ gas = $1.00\times 10^{-6}mmHg=1.32\times 10^{-9}atm$ (1 atm = 760 mmHg)

V = Volume of $N_2$ gas = 985 mL = 0.982 L (1 L = 1000 mL)

n = number of moles $N_2$ = ?

R = Gas constant = $0.0821L.atm/mol.K$

T = Temperature of $N_2$ gas = $0.0^oC=273+0.0=273K$

Now put all the given values in above equation, we get:

$(1.32\times 10^{-9}atm)\times 0.982L=n\times (0.0821L.atm/mol.K)\times 273K$

$n=5.78\times 10^{-11}mol$

Now we have to calculate the number of molecules present in nitrogen gas.

As we know that 1 mole of substance contains $6.022\times 10^{23}$ number of molecules.

As, 1 mole of $N_2$ gas contains $6.022\times 10^{23}$ number of molecules

So, $5.78\times 10^{-11}$ mole of $N_2$ gas contains $(5.78\times 10^{-11})\times (6.022\times 10^{23})=3.48\times 10^{13}$ number of molecules

Therefore, the number of molecules present in nitrogen gas are, $3.48\times 10^{13}$

8 0

3 years ago

In an atomic model that includes a nucleus, positive charge is

olganol [36]

Because protons are positively charged and neutrons have no charge then it is safe to say that such an atomic model would have the positive charge concentrated in the center of an atom (option d).

7 0

3 years ago

Which of the following molecules would have the lowest boiling point?

scZoUnD [109]

The CH4 molecule has the lowest molecular weight, so it has the lowest boiling point.

Hope I helped :)

4 0

3 years ago

5.0 x 10^24 molecules equal

Ratling [72]

4.999999999999999e+24 this is what i got on the calculator but i dont know if its right.

8 0

2 years ago

what is the specific heat of a substance if 1560 cal are required to raise the temperature of a 312-g sample by 15°C

jasenka [17]

Answer:

0.33 cal⋅g-1°C-1

Explanation:

The amount of heat required is determined from the formula:

q= mcΔT

To see more:

https://api-project-1022638073839.appspot.com/questions/what-is-the-specific-heat-of-a-substance-if-1560-cal-are-required-to-raise-the-t#235434

7 0

2 years ago