refrigerator example

For comparison, a simple stylized diagram of a heat pump's vapor-compression refrigeration cycle: 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor

From: https://en.wikipedia.org/wiki/Heat_pump_and_refrigeration_cycle

air conditioner/refrigerator 1

Engine Model

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s.t.p. , r.t.p. and standard conditions

S.T.P, R.T.P. and Standard Conditions in A level chemistry

Some students are confused about the s.t.p. , r.t.p and standard conditions. In this explanation, I would like to express the difference between them. 

1. Definition 

 s.t.p. is expressed as 105 Pa [1 bar] and 273 K [0 °C],  

 r.t.p. is expressed as 101325 Pa [1 atm] and 293 K [20 °C]

Standard condition under new H2 Chemistry syllabus refers to:

• Pressure of 1 bar
• Temperature of 298K
• Substance in its most stable physical form e.g. H₂ (g), H₂O (l), Br₂ (l), NaCl (s), etc

2. Application 

s.t.p and r.t.p are used in calculating the volume of the ideal gas only, and the standard conditions are used to calculate the physical quantities (including enthalpy, entropy, Gibbs Free Energy change, electrode potential and etc. ), which are related to the chemical reactions or processes.