VPJ & ASSOCIATES Interview Questions and Answers

To dilute a 12% NaOH solution to 5%, calculations involve using the formula C1V1 = C2V2 and determining the amount of water needed.

• Use the formula C1V1 = C2V2, where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume.

• Calculate the volume of the initial 12% NaOH solution needed using the formula V1 = (C2 * V2) / C1.

• Subtract the initial volume from the final volume to determine the amount of water needed to dilut...read more

Fire point is the temperature at which a fuel continues to burn after ignition, while flash point is the temperature at which a fuel produces a flammable vapor.

• Fire point is higher than flash point.

• Flash point is the minimum temperature at which a liquid gives off vapor in sufficient concentration to ignite.

• Fire point is the temperature at which a fuel sustains combustion once ignited.

• Flash point is used to classify flammable and combustible liquids.

• Example: Gasoline has a fl...read more

The theoretical plate height in packed bed and distillation columns is a measure of the efficiency of separation.

• The theoretical plate height in packed bed columns is typically calculated using the HETP (Height Equivalent to a Theoretical Plate) equation.

• In distillation columns, the theoretical plate height is a measure of the height of an idealized theoretical plate required for a given separation efficiency.

• Theoretical plate height is influenced by factors such as flow rate...read more

Toxicity refers to the degree to which a substance can damage an organism. LD50 is the lethal dose at which 50% of test subjects die.

• Toxicity is the ability of a substance to cause harm to living organisms.

• LD50 refers to the lethal dose at which 50% of test subjects die when exposed to a substance.

• LD50 is commonly used in toxicology to measure the potency of a substance.

• For example, the LD50 of caffeine in rats is approximately 192 milligrams per kilogram of body weight.

Flash distillation is a single-stage process where a liquid mixture is vaporized quickly, while fractional distillation is a multi-stage process where the mixture is separated into fractions based on boiling points.

• Flash distillation is a rapid vaporization process used for separating components with large differences in boiling points.

• Fractional distillation is a slower process that involves multiple distillation stages to separate components with closer boiling points.

• Flash...read more

The terms 'flammable' and 'inflammable' mean the same thing - capable of catching fire easily.

• Both 'flammable' and 'inflammable' mean easily ignited and capable of catching fire.

• The prefix 'in-' in 'inflammable' does not mean 'not' as in other words, but rather intensifies the meaning.

• The use of 'inflammable' can sometimes cause confusion due to the misconception that it means 'not flammable'.

Different types of permits related to safety include building permits, fire permits, and health permits.

• Building permits are required for construction, renovation, or demolition of buildings to ensure compliance with safety codes.

• Fire permits are necessary for activities involving fire hazards, such as fireworks displays or bonfires.

• Health permits are needed for businesses that handle food or provide health services to ensure hygiene and safety standards are met.