IT IS D FOCAL POINT
P.S. im in middle school not trying to brag
Answer:
At standard room temperature, ![[{\rm OH^{-}] \approx 2.5 \times 10^{-7}\; \rm M](https://tex.z-dn.net/?f=%5B%7B%5Crm%20OH%5E%7B-%7D%5D%20%5Capprox%202.5%20%5Ctimes%2010%5E%7B-7%7D%5C%3B%20%5Crm%20M)
when ![[{\rm H^{+}] = 4.0 \times 10^{-8}\; \rm M](https://tex.z-dn.net/?f=%5B%7B%5Crm%20H%5E%7B%2B%7D%5D%20%3D%204.0%20%5Ctimes%2010%5E%7B-8%7D%5C%3B%20%5Crm%20M)
.
Explanation:
The following equilibrium goes on in water:
.
The forward reaction is known as the self-ionization of water. The ionization constant of water, 
, gives the equilibrium position of this reaction:
![K_{\rm w} = [{\rm H^{+}] \cdot [{\rm OH^{-}}]](https://tex.z-dn.net/?f=K_%7B%5Crm%20w%7D%20%3D%20%5B%7B%5Crm%20H%5E%7B%2B%7D%5D%20%5Ccdot%20%5B%7B%5Crm%20OH%5E%7B-%7D%7D%5D)
.
At standard room temperature (
), 
. Also, ![[{\rm H^{+}}] = 4.0 \times 10^{-8}\; \rm mol \cdot L^{-1}](https://tex.z-dn.net/?f=%5B%7B%5Crm%20H%5E%7B%2B%7D%7D%5D%20%3D%204.0%20%5Ctimes%2010%5E%7B-8%7D%5C%3B%20%5Crm%20mol%20%5Ccdot%20L%5E%7B-1%7D)
. Substitute both values into the equation and solve for ![[{\rm OH^{-}}]](https://tex.z-dn.net/?f=%5B%7B%5Crm%20OH%5E%7B-%7D%7D%5D)
.
![\begin{aligned} {[}{\rm OH^{-}}{]} &= \frac{K_{\rm w}}{[{\rm H^{+}}]} \\ &\approx \frac{10^{-14}}{4.0 \times 10^{-8}} = 2.5 \times 10^{-7}\end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%20%7B%5B%7D%7B%5Crm%20OH%5E%7B-%7D%7D%7B%5D%7D%20%26%3D%20%5Cfrac%7BK_%7B%5Crm%20w%7D%7D%7B%5B%7B%5Crm%20H%5E%7B%2B%7D%7D%5D%7D%20%5C%5C%20%26%5Capprox%20%5Cfrac%7B10%5E%7B-14%7D%7D%7B4.0%20%5Ctimes%2010%5E%7B-8%7D%7D%20%3D%202.5%20%5Ctimes%2010%5E%7B-7%7D%5Cend%7Baligned%7D)
.
In other words, in an aqueous solution at standard room temperature, when .
They are on the left side of the equation.
Answer:
1.3g/L is the density of the air
Explanation:
The room is full of air, the space that the air occupy is:
500 cm x 400 cm x 250 cm = 5.00x10⁷ cm³
The density of a substance is defined as the ratio between the mass of the substance and the space that occupy. We can express the density of air in g/L:
<em>Grams air:</em>
65 kg * (1000g / 1kg) = 65000g
<em>Liters:</em>
5.00x10⁷ cm³ * (1L / 1000cm³) = 50000L
<em>Density:</em>
65000g / 50000L =
<h3>1.3g/L is the density of the air </h3>
