Hazardous Materials Otsu-4 | Physics and Chemistry Calculations: Density, Heat, Concentration, and Flammable Range

Mass equals density multiplied by volume: 0.75 kg/L × 200 L = 150 kg. No further conversion is needed because the volume unit already matches the litre in the density unit. Dividing 200 by 0.75 reverses the density relationship, while 15 kg and 1,500 kg result from misplaced decimal points.

The temperature change is 50 − 20 = 30 K, not the final temperature of 50°C. Substitution into Q = mcΔT gives 2.0 kg × 2.0 kJ/(kg·K) × 30 K = 120 kJ. A Celsius temperature interval and a kelvin interval have the same numerical size; using 50 as ΔT incorrectly gives 200 kJ.

The increase is ΔV = βV₀ΔT = 0.0010 /K × 1,000 L × 30 K = 30 L, giving an approximate final volume of 1,030 L. At least 30 L of calculated free space is therefore required to prevent overflow. Real equipment also needs allowance for temperature distribution, measurement uncertainty, and operating margin.

The solute volumes are 10 L × 0.40 = 4 L and 30 L × 0.20 = 6 L, for a total of 10 L in 40 L of solution. Thus 10 ÷ 40 = 0.25, or 25% by volume. The simple average of 40% and 20% would be valid only for equal solution volumes; here the 20% solution has three times the volume.

Ten percent exceeds the stated upper limit of 8%, but dilution with air necessarily passes through the range from 8% down to 1%. Local regions may enter that range before the average concentration does. Being too rich before ventilation therefore does not establish safety; ignition sources must be controlled in advance, and suitable equipment and concentration monitoring are required.

Nitrogen inerting reduces the oxygen supply needed for combustion and is therefore a smothering action. It neither decomposes the fuel nor works primarily by cooling it. An atmosphere low enough in oxygen to suppress combustion is also hazardous to people. Even without planned tank entry, nitrogen leakage and accumulation can create oxygen deficiency around the tank and must be monitored.

Flash point indicates vapour formation above a liquid surface under a specified test method; it does not categorically exclude the hazard of fine droplets dispersed in air. Even a high-flash-point liquid may ignite as a mist below its flash point when exposed to an electrostatic discharge. Liquid temperature alone does not justify removing static-control measures.

The flame and vessel are not in contact, airflow is almost unchanged, and an intervening screen reduces heat input. These observations identify radiation as the principal blocked pathway. Conduction requires a contacting material path. Convection and conduction may also occur in a real fire, but the stated conditions isolate the contribution of radiation.

At the same temperature, the liquid with the higher vapour pressure has the greater tendency to enter the gas phase. With other conditions equal, vapour generation and accumulation therefore require closer attention for A. Vapour pressure and vapour density are different properties, so a higher vapour pressure does not establish that the vapour is lighter than air. Evaporation also occurs below the boiling point.

One cubic metre equals 1,000 L, so 1.5 m³ equals 1,500 L. The mass is therefore 0.80 kg/L × 1,500 L = 1,200 kg. The key is to convert the volume to litres so that it matches the denominator of the density unit before multiplying; multiplying 1.5 directly by 0.80 mixes incompatible units.