When concentrated sulphuric acid is diluted, the acid is poured slowly into water, never water into acid, because:

The heat released can boil and spatter the mixture

Water and acid react to give off toxic fumes

The final strength would otherwise be wrong

Sulphuric acid floats on top of the water

While making a reagent, a technician splashes 10% sodium hydroxide into one eye. A colleague takes her to the eyewash station. What is the correct first aid?

Irrigate for at least 15 minutes, then see a doctor

Neutralize with dilute acetic acid, then irrigate

Pad the eye and wait for the pain to settle

Irrigate for 1 minute, then neutralize with boric acid

After a needle-stick injury in the laboratory, the first step is to:

Wash the site with soap and running water

Squeeze the wound hard to force out blood

Suck the wound to remove the blood

Scrub the site with undiluted bleach

Laboratory safety and first aid

19 Kerala PSC Lab Technician Gr II practice questions on Laboratory safety and first aid, part of Biochemistry. The first 19 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
When concentrated sulphuric acid is diluted, the acid is poured slowly into water, never water into acid, because:
1. AWater and acid react to give off toxic fumes
2. BThe final strength would otherwise be wrong
3. CThe heat released can boil and spatter the mixture
4. DSulphuric acid floats on top of the water
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Answer: C · The heat released can boil and spatter the mixture
Mixing sulphuric acid with water releases a great deal of heat. If water is added to the acid, the first small amount of water boils at once and throws out hot acid. Adding acid slowly to a larger volume of water, with stirring, in a heat-resistant vessel, lets the water absorb the heat safely. Concentrated sulphuric acid is denser than water, so it sinks and mixes as it is added.
- A: The danger is heat, not toxic gas.
- B: The final concentration is the same whichever order is used.
- D: Concentrated sulphuric acid is denser than water and sinks.
Question 2 · Hard
While making a reagent, a technician splashes 10% sodium hydroxide into one eye. A colleague takes her to the eyewash station. What is the correct first aid?
1. ANeutralize with dilute acetic acid, then irrigate
2. BPad the eye and wait for the pain to settle
3. CIrrigate for at least 15 minutes, then see a doctor
4. DIrrigate for 1 minute, then neutralize with boric acid
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Answer: C · Irrigate for at least 15 minutes, then see a doctor
Alkalis penetrate the eye faster and deeper than most acids and keep damaging it until they are washed away. The eyelids are held open and the eye is flushed with clean running water or saline for at least 15 minutes, longer for alkali, removing any contact lens, and she is then seen urgently by an eye doctor. Neutralizing drops are not used, because the reaction releases heat and wastes time that belongs to irrigation. Padding without irrigation leaves the alkali on the cornea.
- A: Neutralizing in the eye releases heat and delays irrigation.
- B: Padding leaves the alkali in the eye to keep burning.
- D: One minute is far too short, and neutralizing drops are not advised.
Question 3 · Easy
Why was benzidine, once widely used in tests for occult blood, withdrawn from laboratories?
1. AIt is carcinogenic
2. BIt is highly flammable
3. CIt is explosive when dry
4. DIt is strongly corrosive
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Answer: A · It is carcinogenic
Benzidine causes bladder cancer in exposed workers and is a recognized human carcinogen. Occult blood tests now use guaiac or tetramethylbenzidine, which is not regarded as carcinogenic. Carcinogens that must still be used are handled with gloves in a fume hood and clearly labelled. Substitution with a safer chemical is the first choice in controlling any laboratory hazard.
- B: Flammability is the main hazard of solvents such as ether, not of benzidine.
- C: Explosive when dry describes picric acid.
- D: Corrosion is the main hazard of strong acids and alkalis.
Question 4 · Easy
After a needle-stick injury in the laboratory, the first step is to:
1. AWash the site with soap and running water
2. BSqueeze the wound hard to force out blood
3. CSuck the wound to remove the blood
4. DScrub the site with undiluted bleach
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Answer: A · Wash the site with soap and running water
NACO guidelines advise washing the site at once with soap and running water, without scrubbing. Squeezing, sucking or applying bleach or other strong chemicals damages tissue and is not recommended. The exposure is then reported at once so that the source can be assessed and HIV post-exposure prophylaxis, if needed, started as early as possible, preferably within 2 hours and not after 72 hours. Hepatitis B vaccination status is checked at the same time.
- B: Squeezing is discouraged because it injures the tissue around the wound.
- C: Sucking the wound exposes the mouth to the blood.
- D: Bleach and other strong chemicals damage the skin and are not advised.
Question 5 · Medium
Under the CDC universal precautions (1987-88), which body fluid was excluded unless it contained visible blood?
1. ASemen
2. BUrine
3. CPleural fluid
4. DCerebrospinal fluid
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Answer: B · Urine
Universal precautions applied to blood and to fluids linked with bloodborne infection: semen, vaginal secretions, and cerebrospinal, synovial, pleural, peritoneal, pericardial and amniotic fluids. Urine, feces, sputum, nasal secretions, sweat, tears and vomitus were excluded unless visibly bloody, because they carry little risk of HIV or hepatitis B. The later standard precautions dropped this exception and treat every body substance as potentially infectious. Most laboratories now follow standard precautions.
- A: Semen was covered because it can transmit HIV and hepatitis B.
- C: Pleural fluid was one of the covered fluids.
- D: CSF was one of the covered fluids.
Question 6 · Hard
A technician touches a water bath with a frayed cable and collapses, her hand still on the bath. Which sequence is correct?
1. APull her away by the arm, then check breathing
2. BThrow water over her to break the contact
3. CSwitch off the mains, then check breathing
4. DCheck breathing first, then switch off the mains
Answer and explanation in LearnFree account
Question 7 · Easy
A small fire starts inside a colorimeter that is still plugged in. Which extinguisher should be used?
1. ACarbon dioxide
2. BWater
3. CWet chemical
4. DFoam
Answer and explanation in LearnFree account
Question 8 · Easy
Mercury from a broken thermometer is sprinkled with which powder to bind it before collection?
1. ATalc
2. BSulphur
3. CSodium bicarbonate
4. DSawdust
Answer and explanation in LearnFree account
Question 9 · Medium
Concentrated sulphuric acid is spilled on the bench. What should it first be covered with?
1. ASodium hydroxide pellets
2. BSodium bicarbonate
3. CDilute acetic acid
4. DA jet of cold water
Answer and explanation in LearnFree account
Question 10 · Medium
A technician's forearm is scalded by boiling water from a water bath. What is the right first aid?
1. ASmear butter or toothpaste on the burn
2. BApply ice directly to the burned skin
3. CCool it under running tap water for 20 minutes
4. DBurst the blisters and apply antiseptic
Answer and explanation in LearnFree account
Question 11 · Medium
Burning diethyl ether on the bench should not be put out with water because ether:
1. ARaises the water to its boiling point
2. BReacts with water to form an explosive
3. CTurns into a toxic gas with water
4. DFloats on water and spreads the fire
Answer and explanation in LearnFree account
Question 12 · Medium
A tube of blood breaks on the bench. After it is covered with absorbent paper, which disinfectant is poured over it?
1. A1% sodium hypochlorite
2. B70% ethanol
3. C0.1% potassium permanganate
4. DPlain soap solution
Answer and explanation in LearnFree account
Question 13 · Easy
Strong acids, alkalis and infectious fluids should be drawn into a pipette by using:
1. AA rubber bulb or pipetting aid
2. BMouth suction with a cotton plug
3. CMouth suction with a rubber tube
4. DMouth suction through a long pipette
Answer and explanation in LearnFree account
Question 14 · Medium
After an occupational exposure to HIV-positive blood, post-exposure prophylaxis should be started:
1. AAs early as possible, within 72 hours
2. BWithin 2 weeks of the exposure
3. COnly after the worker tests HIV positive
4. DAfter 7 days, once the source is retested
Answer and explanation in LearnFree account
Question 15 · Medium
Why is sputum for mycobacterial culture processed inside a Class II biological safety cabinet?
1. AIt removes acid fumes from the room
2. BIt sterilizes the sample with UV light
3. CIt protects worker, sample and room
4. DIt protects only the sample from dust
Answer and explanation in LearnFree account
Question 16 · Hard
Used Drabkin's reagent from hemoglobin tests is collected in the same waste can as acid waste from a protein test. Shortly after, staff notice a smell of bitter almonds. What is the hazard?
1. ANitrogen dioxide
2. BHydrogen cyanide gas
3. CHydrogen sulphide
4. DChlorine gas
Answer and explanation in LearnFree account
Question 17 · Easy
Which vaccine should every laboratory worker who handles blood receive?
1. ATyphoid vaccine
2. BRabies vaccine
3. CHepatitis B vaccine
4. DHepatitis A vaccine
Answer and explanation in LearnFree account
Question 18 · Easy
By WHO guidance, washing hands with soap and water should take about:
1. A10 minutes
2. B5-10 seconds
3. C2-3 minutes
4. D40-60 seconds
Answer and explanation in LearnFree account
Question 19 · Hard
A laboratory technician who never completed hepatitis B vaccination pricks a finger with a needle used on a patient known to be HBsAg positive. The wound has been washed. Which step should follow?
1. ATest anti-HBs and give nothing if negative
2. BGive hepatitis B vaccine only after 6 months
3. CGive HBIG and start hepatitis B vaccination
4. DStart a 28-day antiretroviral course only
Answer and explanation in LearnFree account

Laboratory safety and first aid

When concentrated sulphuric acid is diluted, the acid is poured slowly into water, never water into acid, because:

While making a reagent, a technician splashes 10% sodium hydroxide into one eye. A colleague takes her to the eyewash station. What is the correct first aid?

Why was benzidine, once widely used in tests for occult blood, withdrawn from laboratories?

After a needle-stick injury in the laboratory, the first step is to:

Under the CDC universal precautions (1987-88), which body fluid was excluded unless it contained visible blood?

A technician touches a water bath with a frayed cable and collapses, her hand still on the bath. Which sequence is correct?

A small fire starts inside a colorimeter that is still plugged in. Which extinguisher should be used?

Mercury from a broken thermometer is sprinkled with which powder to bind it before collection?

Concentrated sulphuric acid is spilled on the bench. What should it first be covered with?

A technician's forearm is scalded by boiling water from a water bath. What is the right first aid?

Burning diethyl ether on the bench should not be put out with water because ether:

A tube of blood breaks on the bench. After it is covered with absorbent paper, which disinfectant is poured over it?

Strong acids, alkalis and infectious fluids should be drawn into a pipette by using:

After an occupational exposure to HIV-positive blood, post-exposure prophylaxis should be started:

Why is sputum for mycobacterial culture processed inside a Class II biological safety cabinet?

Used Drabkin's reagent from hemoglobin tests is collected in the same waste can as acid waste from a protein test. Shortly after, staff notice a smell of bitter almonds. What is the hazard?

Which vaccine should every laboratory worker who handles blood receive?

By WHO guidance, washing hands with soap and water should take about:

A laboratory technician who never completed hepatitis B vaccination pricks a finger with a needle used on a patient known to be HBsAg positive. The wound has been washed. Which step should follow?