neco model questions vol1 2021 chemistry | Practical

Prepare for your exams with neco model questions vol1 questions? Reviewing past/model questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2021 chemistry (Practical) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1 View Details
A mass‑spectrometer was used to analyse a sample of chlorine. The instrument gave the following data: | Isotope | Relative atomic mass (u) | Relative abundance (%) | |---------|--------------------------|------------------------| | ^35Cl | 34.969 | 75.78 | | ^37Cl | 36.966 | 24.22 | Using the data, answer the following questions.
Question Parts
(a)
Calculate the relative atomic mass of chlorine to two decimal places.
(b)
State the number of neutrons present in the most abundant isotope of chlorine.
(c)
Write the ground‑state electron configuration of a neutral chlorine atom.
Detailed Essay Solution & Marking Scheme Available

Get the step-by-step mathematical proofs, key points required by examiners, and a comprehensive breakdown from our AI Tutor.

Reveal Answer
Question 2 View Details
The first ionisation energies (IE) of the elements in the third period were measured and are given in the table below. | Element | Symbol | First IE (kJ mol⁻¹) | |---------|--------|----------------------| | Sodium | Na | 496 | | Magnesium| Mg | 738 | | Aluminium| Al | 578 | | Silicon | Si | 789 | | Phosphorus| P | 1012 | | Sulphur | S | 1002 | | Chlorine| Cl | 1251 | | Argon | Ar | 1521 | Answer the following questions.
Question Parts
(a)
Calculate the average increase in first ionisation energy from sodium to argon across the period.
(b)
Explain the general trend in the values of IE across the period, citing electronic configurations where relevant.
(c)
Predict the first ionisation energy of potassium (K) and justify your prediction using periodic trends.
(d)
Identify any anomalous IE values in the table and provide a brief explanation for each anomaly.
Detailed Essay Solution & Marking Scheme Available

Get the step-by-step mathematical proofs, key points required by examiners, and a comprehensive breakdown from our AI Tutor.

Reveal Answer
Question 3 View Details
A student carried out a series of simple tests on four different substances to investigate the nature of the bonding present. The substances were labelled as follows: - Sample A: Sodium chloride (NaCl) solid dissolved in distilled water. - Sample B: Copper(II) sulfate (CuSO₄·5H₂O) solid dissolved in distilled water. - Sample C: Carbon tetrachloride (CCl₄) liquid placed in a clean dry test tube. - Sample D: A small piece of magnesium ribbon placed in dilute hydrochloric acid (0.10 M HCl). The observations recorded are shown in the table below. | Sample | Conductivity of the solution (if any) | Reaction with dilute HCl (if applicable) | Physical state observed | Flame test colour (if performed) | |--------|----------------------------------------|-------------------------------------------|--------------------------|-----------------------------------| | A | Strong (metallic electrode) | No visible reaction | Clear colourless solution| Yellow‑orange (Na) | | B | Strong (metallic electrode) | No visible reaction | Clear blue solution | Blue‑green (Cu) | | C | No conductivity (no solution) | No reaction (liquid unchanged) | Colourless liquid | No flame test performed | | D | Strong (metallic electrode) after 2 min| Vigorous effervescence, solution becomes colourless | Clear colourless solution| No flame test performed | Using the above data, answer the following:
Question Parts
(a)
Identify the predominant type of chemical bond in each of the four samples (A, B, C and D) and justify your choice with reference to the observations.
(b)
Arrange the samples in order of increasing lattice energy of the solid form of the compounds (excluding the metal) and explain the trend.
(c)
Predict which sample would have the highest boiling point and give a brief reason based on the type of bonding.
Detailed Essay Solution & Marking Scheme Available

Get the step-by-step mathematical proofs, key points required by examiners, and a comprehensive breakdown from our AI Tutor.

Reveal Answer
Question 4 View Details
A gravimetric analysis was carried out to determine the amount of calcium in a sample of unknown composition. The procedure was as follows: 1. A 0.500 g sample of the unknown solid was accurately weighed and transferred to a 250 mL beaker. 2. To the beaker, 100 mL of 0.200 M sodium carbonate solution was added and the mixture was gently heated until a white precipitate of calcium carbonate formed and the solution became clear. 3. The precipitate was filtered, washed with de‑ionised water and dried to constant mass. The mass of the dried CaCO₃ precipitate was recorded as 0.312 g. 4. The dried precipitate was then placed in a crucible and heated strongly in a muffle furnace at 900 °C for 30 min to convert it to calcium oxide (CaO). After cooling in a desiccator, the mass of the CaO obtained was 0.176 g. Using the data above, answer the following questions:
Question Parts
(a)
Calculate the number of moles of CaO obtained after heating.
(b)
From the amount of CaO, determine the number of moles of calcium originally present in the unknown sample.
(c)
Calculate the mass percent of calcium in the original 0.500 g sample.
(d)
Suggest two possible sources of systematic error in this gravimetric determination and explain how each could affect the calculated % Ca.
Detailed Essay Solution & Marking Scheme Available

Get the step-by-step mathematical proofs, key points required by examiners, and a comprehensive breakdown from our AI Tutor.

Reveal Answer

Master the Exam!

You've seen a preview, but there are thousands more questions plus AI tutor to break down complex solutions.

Unlock Full Access Available for Android & Windows
Help others prepare! Share this practice hub:
Chat with Support