Answer:
Limestone caves are formed when acid rain occurs.
Explanation:
When chalk pieces which is made of calcium carbonate react with acetic acid, it produces carbon dioxide, calcium acetate, and water. When calcium carbonate react with Carbonated Water produces calcium bicarbonate. Limestone cave forms when the dissolution of limestone occur when rainwater which is acidic due to the addition of carbondioxide in the air react with limestone. This dissolution removes the lime from the rock and caves are formed.
First, calculate the mass of sodium in g with the help of molar mass and number of moles.
Number of moles =
(1)
Molar mass of sodium =
Substitute the given value of number of moles and molar mass of sodium in formula (1)
(1)
(1)
mass of sodium in g = 
Now, according to conversion factor, 1 g = 1000 mg
So,
of sodium =
=
of sodium
Thus, mass of sodium in mg =
Answer:

Explanation:
The formula for calculating the enthalpy change of a reaction by using the enthalpies of formation of reactants and products is

TiCl₄(g) + 2H₂O(g) ⟶ TiO₂(s) + 4HCl(g)
ΔH°f/kJ·mol⁻¹: -763.2 -241.828 -939.7 -92.307
![\begin{array}{rcl}\Delta_{\text{r}}H^{\circ} & = & [-939.7 + 4(-92.307)] - [-763.2 + 2(-241.828)\\& = & [-939.7 - 369.228] - [-763.2 - 483.656]\\& = & -1308.928 + 1246.856\\& = & \mathbf{-62.1}\\\end{array}\\\text{The amount of heat evolved is } \boxed{\textbf{62.1 kJ}}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Brcl%7D%5CDelta_%7B%5Ctext%7Br%7D%7DH%5E%7B%5Ccirc%7D%20%26%20%3D%20%26%20%5B-939.7%20%2B%204%28-92.307%29%5D%20-%20%5B-763.2%20%2B%202%28-241.828%29%5C%5C%26%20%3D%20%26%20%5B-939.7%20-%20369.228%5D%20-%20%5B-763.2%20-%20483.656%5D%5C%5C%26%20%3D%20%26%20-1308.928%20%2B%201246.856%5C%5C%26%20%3D%20%26%20%5Cmathbf%7B-62.1%7D%5C%5C%5Cend%7Barray%7D%5C%5C%5Ctext%7BThe%20amount%20of%20heat%20evolved%20is%20%7D%20%5Cboxed%7B%5Ctextbf%7B62.1%20kJ%7D%7D)