MITIHANI POPOTE EXAMINATIONS SERIES
FORM FOUR CHEMISTRY EXAMINATION SERIES 2
YEAR: 2022
SECTION A (15 Marks)
Answer all questions in this section
1. For each of the items (i) – (x), choose the correct answer from the given alternatives and write its letter beside the item number in the answer booklets provided.
- What will happen when yellow coloured flowers are placed in a gas jar containing Chlorine gas?
A. Flowers will dry
B. Flowers will change colour to pink
C. There will be decolourization of flowers
D. Flowers will shrink
E. The flower will turn blue
Answer: C
Explanation: Chlorine gas is a strong oxidizing agent that bleaches organic pigments, causing decolourization of the yellow flowers. - A pupil put pieces of glass in water but later wanted to remain only with solvent, what processes can be suitable to obtain solvent?
A. Filtration and condensation
B. Evaporation followed by decantation
C. Evaporation and condensation
D. Filtration
E. Condensation followed by centrifugation
Answer: D
Explanation: Filtration separates the insoluble glass pieces from the water (solvent), leaving pure water behind. - One of the following is a characteristic property of Non-metals.
A. They are electronegative
B. They behave as reducing agent
C. They form cation by gaining electrons
D. They form anions by loss of electrons
E. They are lustrous
Answer: A
Explanation: Non-metals are electronegative, tending to gain electrons to form anions. They are not lustrous and do not form cations by gaining electrons. - The three components of the fire triangle includes the following:
A. Fuel, Air and heat
B. Fuel, hydrogen and heat
C. Fuel, oxygen and heat
D. Fuel, nitrogen and heat
E. Fuel, heat and Carbon
Answer: C
Explanation: The fire triangle consists of fuel, oxygen (from air), and heat, which are essential for combustion. - The dispersed phase of one or more liquid(s) in another liquid is called:
A. Emulsion
B. Suspension
C. An alloy
D. Precipitation
E. Solution
Answer: A
Explanation: An emulsion is a mixture where one liquid is dispersed in another (e.g., oil in water). - Mariam mixed two solutions together in a boiling test tube at 20°C. After mixing the solution the new product was found to have a temperature of 18°C. This shows that the reaction is:
A. An exothermic
B. Neutralization
C. An endothermic
D. Combustion
E. Displacement
Answer: C
Explanation: A temperature decrease indicates an endothermic reaction, as it absorbs heat from the surroundings. - The extraction of iron in the blast furnace gives slag as one of the products, this slag consists of:
A. Molten calcium oxide
B. Molten iron
C. Molten calcium siliconate
D. Molten iron oxide
E. Molten calcium silicate
Answer: E
Explanation: Slag in the blast furnace is molten calcium silicate, formed from calcium carbonate and silica impurities. - In the formation of soil, some soils are younger than others. The main reason for this fact is:
A. The climate of the area
B. The nature of parent rock material
C. Living organism
D. Time in which parent rock is exposed to weathering process
E. The wind blowing in the area
Answer: D
Explanation: The age of soil depends on the duration of weathering of the parent rock, which forms the soil. - Which of the following relates closely in a kinetic nature of matter:
A. Solids appear to be stationary but their particles keep on vibrating
B. At low temperature matter exist in gases form
C. Particles in gaseous state are very close to each other
D. Molecules in liquid state can move in all one fixed direction
E. Particles in solid state are very far compared to gaseous state
Answer: A
Explanation: Solids have particles that vibrate in fixed positions, reflecting the kinetic theory of matter. - Considering the Atomic properties of elements in the periodic table:
A. The first ionization energy increase down a group
B. The Atomic size increases down the group
C. The metallic character increases down a group
D. The atomic radius increases down the group
E. The number of number of shells remains constant down the group
Answer: B, C, D
Explanation: Atomic size, radius, and metallic character increase down a group due to additional electron shells and reduced nuclear attraction. Ionization energy decreases, and the number of shells increases.
2. Match the statement in List A with the respective stage of scientific method in List B by writing the letter of correct response beside the item number in the answer booklet provided.
| List A | List B | Answer |
|---|---|---|
| A statement of how the results relate to hypothesis | A. Conclusion B. Data analysis C. Data collection D. Experimentation E. Hypothesis |
A |
| A series of investigations | D | |
| A statement that identifies an event, fact or situation | C | |
| A tentative explanation | E | |
| A step in which the researcher explains the results | B |
SECTION B (70 Marks)
Answer all questions in this section
3. (a) Indicators behave differently in acidic and basic solutions. Using tabular form, show how different indicators behave in different solutions.
| Indicator | Acidic Solution | Basic Solution |
|---|---|---|
| Litmus | Red | Blue |
| Phenolphthalein | Colourless | Pink |
| Methyl Orange | Red | Yellow |
(b) With the aid of chemical equations, explain the fact that dilute acids react with both metals and metal hydroxides.
- Reaction with Metals: Dilute acids react with reactive metals to produce a salt and hydrogen gas. Example with zinc:
Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)Explanation: Zinc displaces hydrogen from hydrochloric acid, forming zinc chloride and hydrogen gas. - Reaction with Metal Hydroxides: Dilute acids neutralize metal hydroxides to form a salt and water. Example with sodium hydroxide:
NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)Explanation: The acid and base neutralize each other, producing a salt (sodium chloride) and water.
4. (a) A form two student wanted to explain the properties of the sub-atomic particles of an atom. Show how he will have to clarify the properties in the class of 40 students.
| Sub-Atomic Particle | Charge | Mass | Location |
|---|---|---|---|
| Proton | Positive (+1) | 1 amu | Nucleus |
| Neutron | Neutral (0) | 1 amu | Nucleus |
| Electron | Negative (-1) | 1/1836 amu | Orbitals around nucleus |
Explanation: The student should explain that protons and neutrons form the nucleus, contributing most of the atom’s mass, while electrons orbit the nucleus and determine chemical properties.
(b) Explain Dalton’s contribution to Atomic structure.
- Dalton proposed that matter is made of indivisible atoms.
- All atoms of an element are identical in mass and properties.
- Atoms of different elements have different masses and properties.
- Atoms combine in simple whole-number ratios to form compounds.
- Atoms are neither created nor destroyed in chemical reactions.
5. (a) Metals are extracted from their ore. Using three important metals in the table, mention the substance(s) added apart from the important ore and suggest the function(s) of the substance added as in the table.
| Name of Metal to Extract | Substance(s) Added | Function of Substance |
|---|---|---|
| Sodium | Calcium chloride | Lowers melting point of sodium chloride in electrolysis. |
| Aluminium | Cryolite | Lowers melting point of bauxite and acts as a solvent. |
| Iron | Limestone, coke | Limestone forms slag to remove impurities; coke reduces iron oxide. |
(b) Explain why metals higher in the series are extracted by electrolysis and not by chemical reduction.
Metals like sodium and aluminium are high in the reactivity series, meaning they have a strong affinity for oxygen or other elements, making chemical reduction difficult. Electrolysis provides the energy needed to break strong ionic bonds in their ores (e.g., NaCl, Al₂O₃), forcing the metal ions to gain electrons and form pure metal.
6. (a) An employer wanted to produce more Copper in electrolysis for exportation, but he didn’t know what factors to consider so that he can produce more copper. As a young scientist, explain three factors on which the amount of copper deposited will depend.
- Current Strength: Higher current (amperes) increases the rate of copper ion reduction, depositing more copper.
- Time of Electrolysis: Longer duration allows more copper ions to be reduced and deposited.
- Concentration of Electrolyte: Higher copper sulfate concentration provides more Cu²⁺ ions for deposition.
(b) If the amount of Copper that was required to be exported by the employer was 8 kg, calculate the number of Amperes that would be used for 3 hrs.
Given: Mass of copper = 8 kg = 8000 g, Time = 3 hrs = 3 × 3600 = 10800 s, Atomic mass of Cu = 64, Valency of Cu = 2, Faraday’s constant = 96500 C/mol.
Moles of Cu = 8000 / 64 = 125 mol.
Charge (Q) = moles × valency × Faraday’s constant = 125 × 2 × 96500 = 24,125,000 C.
Current (I) = Q / t = 24,125,000 / 10800 ≈ 2234.26 A.
Answer: Approximately 2234.26 Amperes.
7. (a) Nitrates and Carbonates behave differently on heating, using balanced chemical equations show how the nitrate and carbonate of the following elements behave on heating:
- Sodium
Nitrate:2NaNO₃(s) → 2NaNO₂(s) + O₂(g)Carbonate: Sodium carbonate is stable and does not decompose on heating. - Calcium
Nitrate:2Ca(NO₃)₂(s) → 2CaO(s) + 4NO₂(g) + O₂(g)Carbonate:CaCO₃(s) → CaO(s) + CO₂(g)
(b) Explain any three uses of metal nitrates.
- Fertilizers: Nitrates like ammonium nitrate provide nitrogen for plant growth.
- Explosives: Potassium nitrate is used in gunpowder and explosives.
- Preservatives: Sodium nitrate is used in food preservation to prevent bacterial growth.
8. (a) Explain the concept of safety measures for a Chemistry Laboratory.
Safety measures in a chemistry laboratory involve protocols to prevent accidents and ensure safe handling of chemicals and equipment, protecting students and staff.
(b) Explain the significance of each of the following:
- A chemistry laboratory should have safety measures.
Answer: Prevents accidents, injuries, or exposure to hazardous chemicals, ensuring a safe working environment. - It is necessary to familiarize yourself with laboratory apparatus.
Answer: Ensures correct usage, reducing errors and accidents during experiments. - Chemicals in the laboratory must be labelled and stoppered.
Answer: Prevents mix-ups, contamination, or accidental exposure to hazardous substances. - All people working in the laboratory should wear appropriate protective clothes.
Answer: Protects against chemical spills, burns, or inhalation of harmful substances. - Refrigerators and freezers used in the laboratory must be labelled "For chemical use only."
Answer: Prevents contamination of food or medicines with hazardous chemicals.
9. (a) A gift of 5 g of Calcium Carbonate was given to John and 8 g of Calcium Carbonate to Juma. The samples were stored in the same container when John and Juma arrived at home. Next day in the morning their sister Asha accidentally poured dilute hydrochloric acid in the container and a colourless gas R was produced.
- Suggest the name of the colourless gas R produced.
Answer: Carbon dioxide (CO₂). - What chemical test will you conduct to identify gas R?
Answer: Pass the gas through limewater (Ca(OH)₂). If it turns milky due to calcium carbonate precipitation, it confirms CO₂.
CO₂(g) + Ca(OH)₂(aq) → CaCO₃(s) + H₂O(l)
(b) What volume of the gas R was produced?
Total CaCO₃ = 5 g + 8 g = 13 g. Molar mass of CaCO₃ = 100 g/mol.
Moles of CaCO₃ = 13 / 100 = 0.13 mol.
Reaction:
Strategies to Make Your Blog Known in Tanzania
Promoting a blog in Tanzania requires a combination of creating locally relevant content, leveraging digital platforms, and adhering to local regulations. Below are actionable strategies to enhance your blog’s visibility and engagement in Tanzania.
1. Create Locally Relevant and High-Quality Content
- Focus on Tanzanian Interests: Write about topics that resonate with Tanzanians, such as local culture, Swahili literature, travel (e.g., Serengeti, Zanzibar), education, or current events like politics and sports. For example, blogs like Mwananchi gain traction by covering local news.
- Address Local Issues: Create content that educates or solves problems, such as health tips, job opportunities, or climate change solutions. Blogs like Mtemwapoetry succeed by discussing lifestyle and environmental issues.
- Use Swahili and English: Publish in both languages to reach a wider audience. The Michuzi blog gained popularity through Swahili content.
- Ensure Quality: Write well-researched, engaging, and clear posts to build trust and retain readers.
2. Optimize for Search Engines (SEO)
- Use Local Keywords: Include terms like “Tanzania travel,” “Swahili culture,” or “jobs in Dar es Salaam” to attract local search traffic.
- Mobile-Friendly Design: Ensure your blog is responsive, as most Tanzanians access the internet via smartphones.
- Fast Loading: Use a reliable host like Bluehost for quick load times, critical due to connectivity challenges in Tanzania.
- Meta Descriptions and Tags: Write compelling meta descriptions and use relevant tags to improve search visibility.
3. Leverage Social Media and Local Platforms
- Promote on Social Media: Share posts on platforms popular in Tanzania, such as Facebook (e.g., Mwananchi’s 1.6M followers), Instagram, and WhatsApp groups.
- Engage in Forums: Share links on Jamii Forums or local Facebook groups to reach active communities.
- Collaborate with Influencers: Partner with Tanzanian bloggers or social media influencers for cross-promotion.
- Use Visuals: Include high-quality images or videos of Tanzanian culture or landscapes, as seen in the Tanzania Experience blog.
4. Comply with Tanzanian Regulations
- Register Your Blog: Register with the Tanzania Communications Regulatory Authority (TCRA) and pay the ~$930 annual fee to avoid shutdowns, as seen with some blogs.
- Avoid Prohibited Content: Steer clear of content deemed “annoying,” hate speech, or fake news to stay compliant.
- Secure Licensing: Submit forms detailing your blog’s purpose, costs, and growth plans to obtain a license.
5. Build a Community and Engage Readers
- Encourage Interaction: Respond to comments on your blog and social media to foster loyalty, as seen with The Citizen.
- Use Feedback: Incorporate reader suggestions to tailor content, as done by ProBlogger’s Tanzania project.
- Host Contests or Events: Organize online giveaways or meetups in cities like Dar es Salaam to attract readers.
- Email Newsletters: Send regular updates to subscribers to maintain engagement.
6. Overcome Connectivity Challenges
- Optimize for Low Bandwidth: Use compressed images and lightweight themes to ensure fast loading on slow connections.
- Offline Accessibility: Offer downloadable content (e.g., PDFs) for readers in low-connectivity areas.
- Reliable Hosting: Choose providers like Bluehost to minimize downtime.
7. Monetize to Sustain and Grow
- Affiliate Marketing: Partner with local businesses (e.g., safari operators) for commissions.
- Advertisements: Use Google AdSense or local ad networks for revenue.
- Sponsored Posts: Collaborate with Tanzanian brands or tourism boards, as seen with Tanzania Travel Blog.
- Offer Services: Provide consulting or content creation to fund your blog.
8. Network with Other Bloggers
- Join Communities: Connect with bloggers via platforms like FeedSpot or local events.
- Guest Posting: Write for established blogs like TanzaniaInvest or The Blonde Abroad for exposure.
- Attend Events: Participate in media or tech events in Dar es Salaam or Arusha to network.
Conclusion
By creating relevant content, optimizing for SEO, leveraging social media, and complying with Tanzania’s regulations, you can build a popular blog. Engage your community, address connectivity challenges, and explore monetization to sustain growth. Consistency and local relevance are key—learn from successful blogs like Mwananchi, The Citizen, and Tanzania Experience.
No comments
Post a Comment