Fundamental of Material and Energy Balances

A: The right choice locks the balance to a conserved quantity and matches property data without hidden conversions. Option B drags in standard-state assumptions that don't exist in the heater and forces unit gymnastics later. Option C bakes density error straight into the duty once temperature shifts. Option D imports a batch mindset that doesn't map to a steady-state exchanger.

A: The target answer lands at the right order by chaining mass flow, Cp, and ΔT with no phase change. Option B invents vaporization that never happens. Option C drops a zero by slipping from kJ to J mentally. Option D mixes design margin into a raw balance without stating it.

A: The correct pick converts MW to kJ/s and divides by latent heat on the same basis. Option B double-counts heat that's not specified in the duty. Option C slips a decimal by pulling an enthalpy datum that doesn't apply. Option D adds sensible heat that the balance boundary never included.

A: The safe move preserves mass conservation without embedding an assumption that could flip later. Option A elevates a calc sheet over field-controlled documents. Option B does the same but in reverse. Option D hides the inconsistency and guarantees pain during reconciliation.