Answer:
8 gm
Explanation:
NaOH molar weight = 22.989 + 15.999 + 1.008 = 39.996 gm
.5 M would contain 1/2 of this per liter = 19.998 gm
now you only want 400/1000 of a liter = 7.9992 gm ~ 8gm
Answer:
78.04g of 0.448 moles must be added
Explanation:
Using H-H equation we can find the pH of the buffer:
pH = pKa + log [A⁻] / [HA]
<em>Where pH is the pH of the buffer = 7.2</em>
<em>pKa = 7.1</em>
<em>[A⁻] = [K₂HPO₄]</em>
<em>[HA] = [KH₂PO₄]</em>
<em />
Replacing:
7.2 = 7.1 + log [K₂HPO₄] / [KH₂PO₄]
0.1 = log [K₂HPO₄] / [KH₂PO₄]
1.2589 = [K₂HPO₄] / [KH₂PO₄] <em>(1)</em>
<em />
And as the concentration of the buffer is:
1M = [K₂HPO₄] + [KH₂PO₄] <em>(2)</em>
<em></em>
Replacing (2) in (1):
1.2589 = 1M - [KH₂PO₄] / [KH₂PO₄]
1.2589 [KH₂PO₄] = 1M - [KH₂PO₄]
2.2589 [KH₂PO₄] = 1M
[KH₂PO₄] = 0.44M
And [K₂HPO₄] = 0.56M
In 800mL = 0.8L:
0.8L * (0.56mol / L) = 0.448 moles K₂HPO₄. The mass is -Molar mass K₂HPO₄: 174.2g/mol-:
0.448 moles * (174.2g / mol) =
<h3>78.04g of 0.448 moles must be added</h3>
Initial temperature of the gas = 100.0°C + 273 = 373 K
Initial pressure of the gas = 3.0 atm
Final temperature of the gas = 300.0°C + 273 = 573 K
According to Pressure Law,
P₁/T₁ = P₂/T₂
where P₁ and T₁ are the initial pressure and temperature respectively, and P₂ and T₂ are the final pressure and temperature respectively.
Plugging in the given data in Pressure Law we have,
3.0 atm/ 373 K = P₂/573 K
P₂ = (3.0 atm x 573 K)/ 373 K
P₂ = 4.6 atm
Thus, the pressure of the gas at the higher temperature is 4.6 atm.