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)
Answer: The energy of the 4-s subshell is lower than the energy of 3-d subshell.
Explanation:
During the filling of electrons in subshells, the lower energy levels are filled before the higher energy levels. Also known as Aufbau principle.
Energy of the sublevel = (n + l)
where : n = Principal quantum number
l = Azimuthal quantum number(s=0,p=1,d=2,f=3)
Energy of 4-s subshell= (4+0) = 4
Energy of 3-d subshell=(3+2) = 5
Energy of 4-s subshell is lower than the energy of 3-d subshell, that is why 4s orbital is filled before the 3-d subshell.
Answer: The 234.74 grams of sample should be ordered.
Explanation:
Let the gram of 114 Ag to ordered be 
The amount required for the beginning of experiment = 0.0575 g
Time requires to ship the sample = 4.2hour = 252 min(1 hr = 60 min)
Half life of the sample =
= 21 min

![\log[N]=\log[N_o]-\frac{\lambda t}{2.303}](https://tex.z-dn.net/?f=%5Clog%5BN%5D%3D%5Clog%5BN_o%5D-%5Cfrac%7B%5Clambda%20t%7D%7B2.303%7D)
![\log[0.0575 g]=\log[N_o]-\frac{0.033 min^{-1}\times 252 min}{2.303}](https://tex.z-dn.net/?f=%5Clog%5B0.0575%20g%5D%3D%5Clog%5BN_o%5D-%5Cfrac%7B0.033%20min%5E%7B-1%7D%5Ctimes%20252%20min%7D%7B2.303%7D)

The 234.74 grams of sample should be ordered.
Answer:
hope it helps.
Explanation:
Zinc metal dissolves slowly in dilute sulphuric acid to form solutions containing the aquated Zn(II) ion together with hydrogen gas, H2.
Answer: although it is convenient to think of the electron moving around the nucleus along circular paths
Explanation: