Answer: A
Explanation:
A Gold (Au) atom has 79 protons and 79 electrons. A typical gold atom has 118 neutrons, though there are 18 other radioisotopes discovered so far. 79 is its charge (atomic number), which is both its proton number and electron number
Answer: Option (B) is the correct answer.
Explanation:
Expression for the given decomposition reaction is as follows.

Let us assume that x concentration of
is present at the initial stage. Therefore, according to the ICE table,

Initial : x 0
Change : - 0.1 
Equilibrium : (x - 0.1) 0.2
Now, expression for
of this reaction is as follows.

Putting the given values into the above formula as follows.



x = 0.12
This means that
= x = 0.12 atm.
Thus, we can conclude that the initial pressure in the container prior to decomposition is 0.12 atm.
Answer:
The value of Kp at this temperature is 7.44*10⁻³
Explanation:
Chemical equilibrium is established when there are two opposite reactions that take place simultaneously at the same speed.
For the general chemical equation for a homogeneous gas phase system:
aA + bB ⇔ cC + dD
where a, b, c and d are the stoichiometric coefficients of compounds A, B, C and D, the equilibrium constant Kp is determined by the following expression:

Where Px is the partial pressure of each of the components once equilibrium has been reached and they are expressed in atmospheres. The equilibrium constant Kp depends solely on temperature and is dimensionless.
In the case of the reaction:
2 HI (g) ⇔ H₂ (g) + I₂ (g)
the equilibrium constant Kp is determined by the following expression:

The system comes to equilibrium at 425 °C, and
- PHI = 0.794 atm
- PH2 = 0.0685 atm
- PI2 = 0.0685 atm
Replacing:

Kp=7.44*10⁻³
<u><em>The value of Kp at this temperature is 7.44*10⁻³</em></u>
Answer:
2.30 × 10⁻⁶ M
Explanation:
Step 1: Given data
Concentration of Mg²⁺ ([Mg²⁺]): 0.039 M
Solubility product constant of Mg(OH)₂ (Ksp): 2.06 × 10⁻¹³
Step 2: Write the reaction for the solution of Mg(OH)₂
Mg(OH)₂(s) ⇄ Mg²⁺(aq) + 2 OH⁻(aq)
Step 3: Calculate the minimum [OH⁻] required to trigger the precipitation of Mg²⁺ as Mg(OH)₂
We will use the following expression.
Ksp = 2.06 × 10⁻¹³ = [Mg²⁺] × [OH⁻]²
[OH⁻] = 2.30 × 10⁻⁶ M