CBSE Class 11-science Answered

If we consider a linear relation between temperature T and pressure P ,

then let us assume temperature T is given in terms of pressure P as

T = ( a × P ) + b  ...............................(1)

where a and b are constants .

at 0° C pressure P = 75 cm of mercury.  Hence we get

75 a + b = 0  ................................ (2)

at 100° C pressure P = 100 cm of mercury.  Hence we get

100 a + b = 100 ........................(3)

From eqn.(2) and (3) , we get a = 4 , b = -300

Hence eqn.(1) becomes

T = 4 P - 300  ..............................(4)

If we substitute P = 80 cm of mercury , then from eqn.(4) , we get

T = (4 × 80) - 300 = 20° C