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Key Facts: Sri Lanka Scientific Service Exam Exam

2 Papers

Intelligence Test (1 hour) and General Question Paper (3 hours), 100 marks each

SLSS recruitment notification, Gazette of 13.06.2025

50 Questions

Multiple-choice item count of the Intelligence Test paper

SLSS recruitment notification, Gazette of 13.06.2025

40 Marks

Minimum required in each paper to be called for interview

SLSS recruitment notification, Gazette of 13.06.2025

Rs. 1,200

Examination fee, payable online only

SLSS recruitment notification, Gazette of 13.06.2025

22–35 Years

Age limits at the date the notice calling applications is gazetted

SLSS recruitment notification, Gazette of 13.06.2025

0 Marks

Marks awarded at the general interview, which verifies qualifications only

SLSS recruitment notification, Gazette of 13.06.2025

The Sri Lanka Scientific Service Grade III open competitive examination is a two-paper written test — a 50-item Intelligence Test (100 marks, 1 hour) and a General Question Paper (100 marks, 3 hours) — sat in Sinhala, Tamil or English for a Rs. 1,200 fee, requiring at least 40 marks in each paper, with a qualification-verification interview that carries no marks. This independent bank of 100 questions covers scientific and quantitative reasoning, research methodology and laboratory quality systems, current scientific and technological developments, and Sri Lanka's environment, natural resources and science policy.

Sample Sri Lanka Scientific Service Exam Practice Questions

Try these sample questions to review concepts for the Sri Lanka Scientific Service Exam exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1In a biochemical pathway, enzyme E1 converts compound A to B, and enzyme E2 converts B to C. An inhibitor X specifically binds to enzyme E1, preventing its activity. What changes in the concentrations of compounds A, B, and C will occur following the addition of inhibitor X to a steady-state reaction mixture?
A.Concentration of A increases, while concentrations of B and C decrease
B.Concentrations of A, B, and C all increase simultaneously
C.Concentration of A decreases, while concentrations of B and C increase
D.Concentrations of A and B remain constant, while concentration of C decreases
Explanation: Because inhibitor X selectively inactivates enzyme E1, the conversion of substrate A into intermediate B ceases, causing compound A to accumulate and increase in concentration. Meanwhile, downstream enzyme E2 continues to consume the remaining pool of B to produce C until B is depleted, ultimately causing the concentrations of both intermediate B and product C to decrease. This logical pathway deduction reflects standard steady-state metabolic flux control.
2A laboratory analyst performs a two-step serial dilution of a standard stock solution with an initial concentration of 2.0 mol/L. In Step 1, 5.0 mL of stock is diluted with deionized water to a total volume of 50.0 mL. In Step 2, 2.0 mL of the resulting solution is diluted to a total volume of 100.0 mL. What is the final concentration of the analyte?
A.0.020 mol/L
B.0.004 mol/L
C.0.040 mol/L
D.0.002 mol/L
Explanation: In Step 1, the dilution factor is 5.0 mL / 50.0 mL = 1/10, yielding a concentration of 2.0 mol/L × 0.10 = 0.20 mol/L. In Step 2, the dilution factor is 2.0 mL / 100.0 mL = 1/50. Multiplying 0.20 mol/L by 1/50 gives 0.004 mol/L (or 4.0 × 10⁻³ mol/L).
3A bacterial culture growing exponentially has a constant generation (doubling) time of 30 minutes. If the culture initially contains 1.5 × 10³ colony-forming units per milliliter (CFU/mL), what will be the bacterial population density after exactly 3 hours of uninhibited growth?
A.9.6 × 10⁴ CFU/mL
B.4.8 × 10⁴ CFU/mL
C.1.2 × 10⁵ CFU/mL
D.2.4 × 10⁴ CFU/mL
Explanation: Over a period of 3 hours (180 minutes) with a doubling time of 30 minutes, the culture undergoes n = 180 / 30 = 6 generations. The population density is calculated using N = N₀ × 2ⁿ = 1.5 × 10³ × 2⁶ = 1.5 × 10³ × 64 = 96 × 10³ = 9.6 × 10⁴ CFU/mL.
4A chemical compound contains two chiral carbon stereocenters. Stereoisomer P has the configuration (2R, 3R), while Stereoisomer Q has the configuration (2S, 3S), and Stereoisomer R has the configuration (2R, 3S). Based on stereochemical principles, what is the spatial relationship between pairs (P and Q) and (P and R)?
A.P and Q are diastereomers; P and R are enantiomers
B.P and Q are enantiomers; P and R are diastereomers
C.P, Q, and R are all mutually enantiomeric to one another
D.P and Q are structural isomers; P and R are geometric isomers
Explanation: Enantiomers are non-superimposable mirror images that have inverted configurations at all chiral centers; since (2R, 3R) has opposite configuration at both stereocenters compared to (2S, 3S), P and Q are enantiomers. Diastereomers are stereoisomers that are not mirror images, where at least one chiral center is inverted while another remains identical; since P (2R, 3R) and R (2R, 3S) share the same configuration at C2 but differ at C3, they are diastereomers.
5Consider the following statements regarding four metals (W, X, Y, Z) determined from experimental displacement reactions: 1. Metal X displaces metal Y from its sulfate solution. 2. Metal Z displaces metal X from its nitrate solution. 3. Metal W does not displace metal Y from its chloride solution. Which sequence lists these metals in order of decreasing chemical reactivity?
A.Z > X > Y > W
B.W > Y > X > Z
C.X > Z > W > Y
D.Z > Y > X > W
Explanation: A metal can displace another from solution only if it is higher in the electrochemical reactivity series. From premise 1, X > Y. From premise 2, Z > X, establishing Z > X > Y. From premise 3, W cannot displace Y, meaning Y > W. Combining all three deductive deductions yields the unambiguous sequence Z > X > Y > W.
6According to the Beer-Lambert law (A = ε × b × c), a solution of a colored metal complex with a molar absorptivity of 5,000 L/(mol·cm) in a standard 1.00 cm cuvette displays an absorbance of 0.400 at its wavelength of maximum absorption. What is the concentration of the metal complex in this solution?
A.8.0 × 10⁻⁵ mol/L
B.2.0 × 10⁻³ mol/L
C.1.25 × 10⁻⁴ mol/L
D.4.0 × 10⁻⁵ mol/L
Explanation: Rearranging the Beer-Lambert equation gives concentration c = A / (ε × b). Substituting the values gives c = 0.400 / (5,000 L/(mol·cm) × 1.00 cm) = 0.400 / 5,000 = 8.0 × 10⁻⁵ mol/L (or 0.080 mmol/L).
7In a synthesis experiment, 0.50 mol of salicylic acid reacts with excess acetic anhydride to synthesize acetylsalicylic acid (aspirin) according to a 1:1 stoichiometric ratio. If the theoretical molar mass of aspirin is 180.16 g/mol and the actual purified yield obtained is 72.06 g, what is the percentage yield of the reaction?
A.80.0%
B.72.0%
C.85.5%
D.90.0%
Explanation: The theoretical yield in moles is 0.50 mol. The theoretical yield in mass is 0.50 mol × 180.16 g/mol = 90.08 g. Percentage yield = (Actual Yield / Theoretical Yield) × 100% = (72.06 g / 90.08 g) × 100% = 80.0%.
8A researcher investigates the effect of ambient humidity on plant transpiration rate by placing four identical potted plants under sealed glass bell jars with relative humidity maintained at 20%, 40%, 60%, and 80% respectively. However, the 20% humidity jar is placed directly adjacent to an incandescent lamp that emits significant radiant heat, while the other three jars are shielded from direct thermal radiation. Why is the conclusion regarding humidity invalid?
A.Transpiration rates cannot be measured inside enclosed glass bell jars
B.Temperature acted as an uncontrolled confounding variable that varied systematically with humidity
C.Four test plants provide too small a sample size to measure any biological phenomenon
D.Relative humidity does not exert any physical influence on stomatal vapor pressure deficits
Explanation: In experimental design, valid attribution requires isolating the independent variable while keeping all other potential factors constant. Because the 20% humidity chamber was subjected to elevated radiant heat from the lamp, its temperature was higher than the other chambers. Since temperature directly alters leaf vapor pressure deficit and stomatal conductance, temperature acts as an uncontrolled confounding variable, making it impossible to attribute observed transpiration differences solely to relative humidity.
9Consider the following biological premises: Premise 1: All active globular enzymes possess a specific tertiary conformation maintained by non-covalent interactions. Premise 2: Temperatures exceeding 70 °C disrupt non-covalent hydrogen and ionic bonds in mesophilic proteins. Premise 3: Salivary amylase is a mesophilic globular enzyme. Which conclusion is logically guaranteed by these premises?
A.Salivary amylase will denature and lose catalytic activity when heated above 70 °C
B.Salivary amylase will accelerate its catalytic rate indefinitely above 70 °C
C.Salivary amylase will form covalent peptide bonds when exposed to temperatures exceeding 70 °C
D.All enzymes in hyperthermophilic bacteria will denature at 70 °C
Explanation: Through standard deductive syllogism, because salivary amylase is a mesophilic globular enzyme whose functional tertiary structure relies on non-covalent interactions, and temperatures above 70 °C disrupt these non-covalent bonds, salivary amylase will undergo conformational denaturation and lose catalytic activity at temperatures above 70 °C.
10In an enzyme kinetics study using a Lineweaver-Burk double reciprocal plot (1/V versus 1/[S]), the addition of inhibitor Z causes the plotted line to pivot upwards around the identical y-intercept (1/V_max), while shifting the x-intercept (-1/K_m) closer to the origin (less negative). What type of inhibition does compound Z exhibit, and how are the kinetic parameters affected?
A.Competitive inhibition; V_max remains unchanged and apparent K_m increases
B.Non-competitive inhibition; V_max decreases and K_m remains unchanged
C.Uncompetitive inhibition; both V_max and K_m decrease by equal proportions
D.Irreversible inhibition; V_max decreases and apparent K_m decreases
Explanation: In a Lineweaver-Burk plot, the y-intercept is 1/V_max and the x-intercept is -1/K_m. When an inhibitor leaves the y-intercept unchanged, V_max is unaltered. When the x-intercept shifts towards zero (e.g., from -2.0 to -1.0), the magnitude of 1/K_m decreases, meaning that apparent K_m has increased. This diagnostic pattern—unchanged V_max and increased K_m—uniquely characterizes competitive inhibition, where substrate and inhibitor compete for the free active site.

About the Sri Lanka Scientific Service Exam Exam

The Open Competitive Examination for Recruitment to the Posts Which Have Fallen Vacant in Grade III of the Sri Lanka Scientific Service is the entry route for science graduates into scientific officer, research officer and laboratory specialist posts across state departments, statutory research bodies and scientific ministries. Appointments are governed by the Scientific Service Minute published in Gazette Extraordinary No. 1877/27 of 28 August 2014 and by the Procedural Rules of the Public Service Commission published in Gazette Extraordinary No. 2310/29 of 14 December 2022. The 2025 cycle was called by a notification in Part I Section (IIA) of the Gazette of 13 June 2025 for 95 vacancies, with the examination held in Colombo in September 2025. Candidates apply for several posts at once and state an order of preference, and the written examination is common to all of them.

Exam sponsor: Conducted by the Commissioner General of Examinations subject to the terms of the Public Service Commission, which is the Appointing Authority.. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Two written papers totalling 200 marks, conducted by the Commissioner General of Examinations: Paper 1, Intelligence Test (100 marks, 1 hour, 50 multiple-choice questions on critical reasoning, general intelligence and decision making) and Paper 2, General Question Paper (100 marks, 3 hours) testing understanding of the political, social, cultural and economic environment of Sri Lanka, matters currently important nationally and internationally, and national and international scientific and technical development. Candidates scoring 40% or more in each paper are interviewed in order of marks by a board approved by the Public Service Commission purely to verify qualifications; no marks are awarded there. Appointment to each post follows the preference stated on the application and the order of aggregate written marks.

Time Limit

4 hours total across two papers.

Passing Score

At least 40 marks in each written paper; selection strictly by the aggregate of written marks, as the interview carries no marks.

Exam / Certification Fees

Rs. 1,200.00, payable only through the online payment methods set out in the Gazette notification.

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

100 marks (Paper I)

Intelligence & Scientific Reasoning

Scientific logical deductions, spatial geometry, interpreting data trends from scientific tables and graphs, quantitative relational problems, and hypothesis testing.

50 marks (General Paper component)

Scientific Research Methodology & Laboratory Quality

Experimental controls, sampling methods, systematic vs random errors, standard error of the mean, calibration curves, ISO/IEC 17025 accreditation, biosafety levels, and ethical publishing standards.

25 marks (General Paper component)

National & International Scientific Advancements

Genetic editing (CRISPR), carbon capture, green hydrogen, photovoltaic innovations, AI in structural biology, quantum computing, and international disease surveillance networks.

25 marks (General Paper component)

Sri Lankan Environment, Natural Resources & Science Policy

Wet and dry zone agro-ecological zoning, Sinharaja and central highlands biodiversity, vein graphite and mineral sands mining, Mahaweli river basin hydrology, the National Environmental Act, and national STI roadmap directives.

Preparing for the Sri Lanka Scientific Service Exam Exam

What You Need to Know

  • Passing score: At least 40 marks in each written paper; selection strictly by the aggregate of written marks, as the interview carries no marks.
  • Assessment: Two written papers totalling 200 marks, conducted by the Commissioner General of Examinations: Paper 1, Intelligence Test (100 marks, 1 hour, 50 multiple-choice questions on critical reasoning, general intelligence and decision making) and Paper 2, General Question Paper (100 marks, 3 hours) testing understanding of the political, social, cultural and economic environment of Sri Lanka, matters currently important nationally and internationally, and national and international scientific and technical development. Candidates scoring 40% or more in each paper are interviewed in order of marks by a board approved by the Public Service Commission purely to verify qualifications; no marks are awarded there. Appointment to each post follows the preference stated on the application and the order of aggregate written marks.
  • Time limit: 4 hours total across two papers.
  • Exam / certification fees: Rs. 1,200.00, payable only through the online payment methods set out in the Gazette notification. Official sources

Using Our Practice Resources

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

Sri Lanka Scientific Service Exam: Suggested Study Strategy

1Master ISO/IEC 17025 concepts and basic statistical calculations including standard deviation, standard error of the mean, confidence intervals, and linear calibration regression lines.
2Review Sri Lankan environmental legislation thoroughly, focusing on the National Environmental Act No. 47 of 1980, the functions of the Central Environmental Authority (CEA), and environmental impact assessment (EIA) protocols.
3Practice rapid graphical interpretation and logical deductive puzzles daily to build the speed and precision required for the 50-item, 60-minute Intelligence Test.

Frequently Asked Questions

What is the structure of the Sri Lanka Scientific Service Grade III examination?

Two written papers of 100 marks each. Paper 1 is a one-hour Intelligence Test of 50 multiple-choice questions on critical reasoning, general intelligence and decision making. Paper 2 is a three-hour General Question Paper testing general knowledge — the political, social, cultural and economic environment of Sri Lanka, matters currently important nationally and internationally, and national and international scientific and technical development — with Part One short questions worth 25 marks and Part Two semi-structured questions worth 75 marks, answering five of eight. A candidate must score at least 40 marks in each paper.

What educational qualifications are required to apply for the SLSS Open Examination?

Qualifications are prescribed post by post in the Gazette notification, because the service covers posts in many ministries and departments. Most require a four-year B.Sc. Special or Honours degree with a class in the relevant science from a university recognised by the University Grants Commission or an institution the UGC recognises as degree awarding; several posts alternatively accept a B.Sc. general degree including the subject together with a relevant postgraduate degree. Applicants must be Sri Lankan citizens aged 22 to 35 on the date the notice is gazetted.

How are candidates selected for appointment to Grade III scientific officer posts?

Candidates scoring 40 marks or more in each paper are called for a general interview in order of marks. That interview is held strictly to verify qualifications and no marks are awarded at it, so appointment to each post follows the preferences stated on the application and the order of aggregate written marks. Where candidates tie for the last remaining vacancies, the Public Service Commission may apply a further special selection process consisting of a written test and a competency-based interview.

Is this practice bank officially affiliated with the Public Service Commission or the Department of Examinations?

No. This is independent Sri Lanka Scientific Service practice by OpenExamPrep, written to cover the reasoning and general-knowledge areas the examination tests. It is neither published nor endorsed by the Department of Examinations or the Public Service Commission and contains no past paper material. The Intelligence Test paper is itself 50 multiple-choice questions, so that half of the examination matches this format closely; the General Question Paper, however, is answered in short and semi-structured writing in Sinhala, Tamil or English, so this English-language multiple-choice bank is a study adaptation of that paper's subject matter rather than a simulation of it.