Correct Answer: B. Fe2O₃

Correct Answer: D) 0.40

Explanation

To calculate the number of moles in 7.20g of H\(_2\)O, we first need to find the molar mass of H\(_2\)O. The molar mass is the sum of the atomic masses of all the atoms in the compound. In this case, H\(_2\)O consists of two hydrogen atoms (H) and one oxygen atom (O).

The atomic mass of hydrogen is approximately 1g/mol, and the atomic mass of oxygen is approximately 16g/mol. So, the molar mass of H\(_2\)O is:

Now, we can use the formula for calculating the number of moles:

Substitute the given mass (7.20g) and the molar mass of H\(_2\)O (18g/mol) into the formula:

Perform the calculation:

So, there are0.40 moles of H\(_2\)O in 7.20g of the compound, which corresponds toOption D.

Correct Answer: A. diffusion

Correct Answer: C) NO₂

Explanation

When copper metal is added to concentrated trioxonitrate (v) acid, it dissolves and releases a gas. The question is asking which gas is released. The options are CO₂, SO₂, NO₂ and CO.

CO₂ is carbon dioxide, which is a gas formed from carbon and oxygen. SO₂ is sulfur dioxide, which is a gas formed from sulfur and oxygen. CO is carbon monoxide, which is a gas formed from carbon and oxygen.

The correct answer is option C, NO₂, which is nitrogen dioxide. Nitrogen dioxide is a reddish-brown gas that is formed when nitrogen and oxygen react at high temperatures, and it is released when copper metal dissolves in concentrated trioxonitrate (v) acid.

It is important for students to understand the properties of acids and bases, how they react with metals, and the gases that are produced when some metals react with acids. This knowledge is important in understanding the chemical reactions that occur in the environment and in industrial processes.

For more information, please see the recommended textbooks.

Explanation

(a) A catalyst functions effectively within a narrow range of temperature. A catalyst also functions effectively within narrow range of pH. A catalyst works on specific reactions.

(b)(i) Iron is applied as catalyst in the Haber's process.

(ii) Ethyne is converted into ethane over nickel as catalyst.

(iii) Decomposition of hydrogen peroxide over platinum.

(c) An enzyme called zymase is an organic catalyst which work on glucose to ethanol.

Explanation

a)(i) Caesium(Cs)

(ii) Gold (Au)

(b) Solution Y has been oxidized to iron (III) salts and it will give a reddish brown precipitate with excess sodium hydroxide.

Correct Answer: B. 0.579

Correct Answer: A) 0.05

Explanation

First, we need to determine the number of moles of bromine (Br₂) that are produced. We can do this by using the molar volume of gas at standard temperature and pressure (s.t.p.), which is 22.4 dm³/mol.

To find the moles of Br₂, we can use the formula:

\[\text{moles of Br}_2 = \frac{\text{volume of Br}_2}{\text{molar volume of gas at s.t.p.}}\]

Plugging in the given values:

\[\text{moles of Br}_2 = \frac{0.56 \ \text{dm}^3}{22.4 \ \text{dm}^3/\text{mol}} = 0.025 \ \text{mol}\]

Now, we need to determine the number of moles of electrons required for the half-cell reaction. The balanced half-cell reaction is:

2Br^- \(\rightarrow\) Br₂ + 2e^-

This means that 2 moles of electrons are required for every 1 mole of Br₂ produced. So, we can find the moles of electrons needed by multiplying the moles of Br₂ by 2:

\[\text{moles of electrons} = 0.025 \ \text{mol} \times 2 = 0.05 \ \text{mol}\]

Therefore, 0.05 moles of electrons will be required to produce 0.56 dm³ of bromine at s.t.p., making Option A the correct answer.

Correct Answer: D) an oxime

Explanation

A ketone is an organic compound containing a carbonyl group (C=O) bonded to two alkyl groups. When a ketone reacts with hydroxylamine (NH₂OH), it forms a compound called an oxime.

Here is the general reaction for a ketone (R₁CO-R₂) reacting with hydroxylamine:

\(R_1CO-R_2 + NH_2OH \rightarrow R_1C(NOH)-R_2 + H_2O\)

In this reaction, the carbonyl group (C=O) of the ketone reacts with the hydroxylamine to form a new compound with a C=N-OH group, which is the characteristic functional group of an oxime. The other products of the reaction are water (H₂O).

Therefore, the correct answer isOption D: an oxime.

Some other options mentioned are not formed during this reaction:

• Hydrazone - formed when a ketone reacts with a hydrazine (NH₂-NH₂).
• Alkanonitrile - contains a cyano group (C?N) and is not formed by the reaction of a ketone with hydroxylamine.
• Nitroso compound - contains a nitroso group (N=O) and is not formed by the reaction of a ketone with hydroxylamine.

Explanation

(a)i. Its colour darkens from pale yellow to amber colour while its crystals become needle-like and at 119oC it begins to melt.

ii. The solution turns green, bubbles of colourless gas rise from the bottom of the mixture, but brown fumes of NO2 are produced and the solutions later turns blue.

(b)i - SO2

- CO2

- CO

- NO2

- H2S

ii. Methane

iii. - Contamination of soil

- Soil erosion

- Contamination of ground water

- Loss of biodiversity

- Formation of sink holes

iv. Because of the large surface area and the higher the area the faster the rate of reaction.

v. Coke

(c)i. The sample is added to anhydrous copper (II) tetraoxosulphate (VI) when it turns from white to blue confirms the presence of water/sample is added to anhydrous cobalt chloride/cobalt chloride paper when it turns from blue to pink indicates the presence of water.

ii(a) It softens temporary hard water

(b) To remove permanent hardness/soften hard water

iii. - Ca(HCO3)2 ---heat--->CaCO3 + CO2 + H2O + H2O

or

Mg(HCO3)2 ---heat--->MgCO3 + CO2 + H2O + H2O