A specific amount of energy is emitted when excited electrons in an atom in a sample of an element return to the ground state.Th

Answer:

Below are the downsides of each electron configuration model:

1). Dot Structures - They consume more space and fail to convey the electron distribution within orbitals.

2). Arrow and line diagrams complicate electron counting and also take up excessive space.

3). Written Configurations do not illustrate electron distribution in orbitals, leading to possible errors in counting electrons.

A negative formation enthalpy indicates that the reaction releases heat during the process.
(C,)

Answer:

9.88

Explanation:

The higher the Ksp, the more soluble a compound is. Hence, Co(OH)₂ ranks as the least soluble hydroxide.

Its maximum concentration must be 1x10⁻⁶ M, and the reaction can be represented as:

Co(OH)₂(s) ⇄ Co⁺²(aq) + 2OH⁻(aq)

Thus, [Co⁺²] = 1x10⁻⁶M

Ksp =  [Co⁺²] *[OH⁻]²

[[OH⁻]² = 5.9x10⁻¹⁵/1x10⁻⁶

[[OH⁻] = √(5.9x10⁻⁹)

[[OH⁻] = 7.6811x10⁻⁵

pOH = -log[OH⁻]

pOH = -log(7.6811x10⁻⁵)

pOH = 4.11

Knowing that pH + pOH = 14

pH = 14 - 4.11

pH = 9.88

Explanation:

5.5 billion grains of sand (5.5×10^9 grains)

Assuming the amount of brown sand is 6.0%, how many brown grains are found in the bucket?

Grains of brown sand = Percentage of brown sand * Total sand in the bucket

Calculated brown grains = 0.06 * 5.5×10^9 = 0.33 x 10^9 = 3.3 x 10^8 grains

If the concentration of brown sand is 6.0 ppm, what is the number of brown grains in the bucket?

Grains of brown sand = Concentration of brown sand * Total sand in the bucket

6 ppm = 6 / 1,000,000 = 0.000006

Calculated brown grains = 0.000006 * 5.5×10^9 = 3.3 x 10^4 grains

If the concentration of brown sand is 6.0 ppb, how many brown grains exist in the bucket?

Grains of brown sand = Concentration of brown sand * Total sand in the bucket

6 ppb = 6 / 1,000,000,000 = 0.000000006

Calculated brown grains = 0.000000006 * 5.5×10^9 = 3.3 x 10^1 = 33 grains

The answer is D. Aluminium Oxide 0.10, Magnesium Oxide 0.50. Firstly, for sodium hydroxide, we can calculate the number of moles using the formula moles = concentration × volume, leading to 0.2 moles from 100 cm³ at 2 moldm-3. Since 2 moles of NaOH yield 1 mole of Al2O3, this means 0.2 moles of NaOH produces 0.1 moles of Al2O3. For hydrochloric acid, moles can similarly be determined, leading to 1.6 moles from 800 cm³ at 2 moldm-3. Considering that 1 mole of Al2O3 reacts with 6 moles of HCl, 0.1 moles of Al2O3 will consume 0.6 moles of HCl. Post-reaction, we have 1 mole of HCl remaining, which will further react with magnesium oxide, thereby yielding 0.5 moles of MgO.