Correct Answer: D. 5

Explanation

There are 5 unpaired electrons present in \(_{26}Fe^{3+}\).

The atomic number of iron is 26, so it has 26 electrons. When iron loses 3 electrons to form \(Fe^{3+}\), it loses 2 from the s orbital and 1 from the d orbital. This leaves 5 unpaired electrons in the d orbital.

The electron configuration of \(Fe^{3+}\) is [Ar]3d5. The 5 d electrons are all unpaired because Hund's rule states that electrons will occupy degenerate orbitals singly before they pair up. This is because unpaired electrons have a lower energy than paired electrons.

Correct Answer: B. metallic bonds

Explanation

In metallic bonding, positive metal ions (cations) are surrounded by a sea of delocalized electrons that move freely throughout the metal lattice. This arrangement creates a cohesive force that holds the metal atoms together. The mobile electrons contribute to the unique properties of metals, such as high electrical and thermal conductivity, malleability, and ductility.

Correct Answer: C. flooding

Explanation

Flooding is a major consequence of global warming because as the Earth's ice caps and glaciers melt, sea levels rise. This can cause flooding in coastal areas and low-lying islands. For example, in 2019, the Netherlands experienced its worst flooding in decades, with over 10,000 homes damaged and thousands of people evacuated.

Correct Answer: B. 0.74 mol dm^-3

Explanation

Molar mass of Na2SO4 = 2(Na) + S + 4(O) = 2(23.0 g/mol) + 32.1 g/mol + 4(16.0 g/mol) = 46.0 g/mol + 32.1 g/mol + 64.0 g/mol = 142.1 g/mol

Now, we can calculate the number of moles of Na2SO4 in the solution:

Number of moles = Mass of the salt / Molar mass

Number of moles = 10.5 g / 142.1 g/mol ≈ 0.0739 mol

Next, we need to find the volume of the saturated solution, given as 100 cm³, and convert it to liters:

Volume of solution = 100 cm³ = 100 cm³ / 1000 cm³/dm³ = 0.1 dm³

Finally, we can calculate the solubility in mol/dm³:

Solubility = Number of moles / Volume of solution

Solubility = 0.0739 mol / 0.1 dm³ ≈ 0.739 mol/dm³

Rounded to two decimal places, the solubility of sodium tetraoxosulphate (VI) at 30°C is approximately 0.74 mol/dm³.

Therefore, the correct option is:

0.74 mol dm-3.

Solubility = 10.5 g / 100 cm3 * 142 g/mol = 0.739 mol/dm3

Correct Answer: D. 30

Explanation

Molar mass of \(C_2H_4O_2\),= (12 × 2) + (1 × 4) + (16 × 2)= 60 g/mol

Vapour density = RMM/2

=60/2=30

Correct Answer: B. melting point increases

Explanation

Melting point increases. This is because the atoms become larger as you go down the group, which means that the metallic bonds between them become stronger.

Explanation

ai. \(H_2SO_4 + 2NaOH → Na_2SO_4 + 2H_2O\)

ii. Concentration of NaOH(\(C_n)\)

\(C_n\) = 4/40= 0.1 mol/\(dm^3\)

\(\frac{C_AV_A}{C_nV_n} = \frac{1}{2}\)

\(C_A \times \frac{8}{0.1} \times 20 = \frac{1}{2}\)

\(C_A =0.1 \times 20 \times \frac{1}{2} \times 8 = 0.125 mol /dm^3\)

bi. -The volume of a gas is negligible compared to the total volume of the container

-There are no forces of attraction or repulsion between molecules of the gas/collision between molecules is elastic.

ii. The volume of a gas is not negligible because at high pressure the molecules occupy appreciable volume and at low temperature the

intermolecular forces of attraction and repulsion become significant.

ci. Glucose.

ii. -Fructose

-Galactose

iii. hydrolysis

iv. 2(\(C_6H_{10}O_5)_n + nH_2O → nC_{12}H_{12}O_{11}\)

\(C_{12}H_{12}O_{11} + H_2O → 2C_6H_12O_6\)

v. -maltase

-diastase

d. It Is the existence of compounds with the same molecular formula but different structural formulae/arrangement of the atoms/linkage of the atoms.

Correct Answer: A. nitrogen

Explanation

The density of a gas is directly proportional to its molar mass. This means that gases with a lower molar mass will be less dense than gases with a higher molar mass. Nitrogen (N2) has a molar mass of 28 g/mol, which is less than that of air (approximately 29 g/mol), making it less dense than air.

Correct Answer: D. 0.80 g

Explanation

Amount (in moles) = Molarity × Volume

Amount (in moles) = 0.20 mol/dm³ × 100.0 cm³ / 1000 cm³/dm³ = 0.020 moles

Now, we can calculate the mass using the formula:

Mass = Amount × Molar Mass

Mass = 0.020 moles × 40.0 g/mol = 0.80 g

So, the correct answer is:0.80 g

Correct Answer: A. HF,\(NH_3\), \(SiH_4\), \(CH_4\)

Explanation

The correct order of boiling points of the compounds \(NH_3\), HF, \(SiH_4\), and \(CH_4\) is HF, \(NH_3\), \(SiH_4\), \(CH_4\).

The correct order of boiling points of the compounds \(NH_3\), HF, \(SiH_4\), and \(CH_4\) is HF, \(NH_3\), \(SiH_4\), \(CH_4\).

The boiling point of a compound is the temperature at which the vapor pressure of the liquid is equal to the atmospheric pressure. The stronger the intermolecular forces, the higher the boiling point.