The mantle has a mass of around
that is around 68.4% of earth's mass.
So to calculate moles we need to first find out the mass of oxygen and silicon present in mantle. It is given that oxygen is 44.8% by mass in mantle and 21.5% by mass in mantle, therefore to calculate its mass, we need to use ![\text{mass percentage }=\frac{\text{mole of solute}}{\text{mass of solution}}\times100](https://tex.z-dn.net/?f=%5Ctext%7Bmass%20percentage%20%7D%3D%5Cfrac%7B%5Ctext%7Bmole%20of%20solute%7D%7D%7B%5Ctext%7Bmass%20of%20solution%7D%7D%5Ctimes100)
Now, to calculate mass percentage of oxygen
![44.8 =\frac{x}{4.278X10^2^4kg}\times100](https://tex.z-dn.net/?f=44.8%20%3D%5Cfrac%7Bx%7D%7B4.278X10%5E2%5E4kg%7D%5Ctimes100)
![x= 191.65\times10^2^2kg](https://tex.z-dn.net/?f=x%3D%20191.65%5Ctimes10%5E2%5E2kg)
Similarly the mass of silicon can be calculated
![x=91.977\times10^2^2kg](https://tex.z-dn.net/?f=x%3D91.977%5Ctimes10%5E2%5E2kg)
Now, the moles of any substance is calculated by
![\text{moles}= \frac{\text{given mass}}{\text{molar mass}}](https://tex.z-dn.net/?f=%5Ctext%7Bmoles%7D%3D%20%5Cfrac%7B%5Ctext%7Bgiven%20mass%7D%7D%7B%5Ctext%7Bmolar%20mass%7D%7D)
![\text{moles of oxygen}= \frac{191.65\times10^2^2kg}{2.6566962\times10^-^2^6kg}](https://tex.z-dn.net/?f=%5Ctext%7Bmoles%20of%20oxygen%7D%3D%20%5Cfrac%7B191.65%5Ctimes10%5E2%5E2kg%7D%7B2.6566962%5Ctimes10%5E-%5E2%5E6kg%7D)
where, mass of oxygen in kilograms is ![2.6566962\times10^-^2^6kg](https://tex.z-dn.net/?f=2.6566962%5Ctimes10%5E-%5E2%5E6kg)
So,![\text{moles of oxygen}=72.1384\times10^4^8\text{moles of O}](https://tex.z-dn.net/?f=%5Ctext%7Bmoles%20of%20oxygen%7D%3D72.1384%5Ctimes10%5E4%5E8%5Ctext%7Bmoles%20of%20O%7D)
Similarly ![\text{moles of silicon}= \frac{91.977\times10^2^2kg}{4.663\times10^-^2^6kg}](https://tex.z-dn.net/?f=%5Ctext%7Bmoles%20of%20silicon%7D%3D%20%5Cfrac%7B91.977%5Ctimes10%5E2%5E2kg%7D%7B4.663%5Ctimes10%5E-%5E2%5E6kg%7D)
![\text{moles of silicon}=19.724\times10^4^8\text{moles of Si}](https://tex.z-dn.net/?f=%5Ctext%7Bmoles%20of%20silicon%7D%3D19.724%5Ctimes10%5E4%5E8%5Ctext%7Bmoles%20of%20Si%7D)
Now, to calculate mole ratio we need to divide every moles to the lowest calculated mole that is the moles of Si and round it off to the nearest whole number.
![\text{mole ratio of oxygen}= \frac{72.138\times10^4^8kg}{19.724\times10^4^8kg}](https://tex.z-dn.net/?f=%5Ctext%7Bmole%20ratio%20of%20oxygen%7D%3D%20%5Cfrac%7B72.138%5Ctimes10%5E4%5E8kg%7D%7B19.724%5Ctimes10%5E4%5E8kg%7D)
![=3.65\approx 4](https://tex.z-dn.net/?f=%3D3.65%5Capprox%204)
![\text{mole ratio of Silicon}=\frac{19.724\times10^4^8}{19.724\times10^4^8}](https://tex.z-dn.net/?f=%5Ctext%7Bmole%20ratio%20of%20Silicon%7D%3D%5Cfrac%7B19.724%5Ctimes10%5E4%5E8%7D%7B19.724%5Ctimes10%5E4%5E8%7D)
![=1](https://tex.z-dn.net/?f=%3D1)
![\text{Mole ratio of Oxygen : Mole ratio of Silicon} = 4:1](https://tex.z-dn.net/?f=%5Ctext%7BMole%20ratio%20of%20Oxygen%20%3A%20Mole%20ratio%20of%20Silicon%7D%20%3D%204%3A1)
Answer:chemical change is irreversible?
Explanation:
<u>Answer:</u> D. the ionic compound calcium fluoride ![(CaF_2)](https://tex.z-dn.net/?f=%28CaF_2%29)
The correct option here is the fourth one.
<u>Explanation:</u>
Salt like compounds addition to water is likely to be inducing certain changes in temperature of freezing into solid and also alter the temperature of boiling.
It is noticed that addition of salts in water mostly tends to get lower the freezing temperatures from the original freezing point of water and among the given 3 options calcium fluoride tends to lower the freezing point most when compared to others.
Thus as vant hoff factor is highest factor for
and the freezing point will be lowest.