Distinguish(solid, liquid, gas)

Explanation:

A solid, at a given temperature, has a definite volume  

and shape which may be affected by changes in  

temperature. Solids usually increase slightly in size  

when heated (expansion)  and usually  

decrease in size if cooled (contraction).A liquid, at a given temperature, has a  

fixed volume and will take up the shape of any  

container into which it is poured. Like a solid, a  

liquid’s volume is slightly affected by changes in  

temperature.

A gas, at a given temperature, has neither a definite  

shape nor a definite volume. It will take up the shape  

of any container into which it is placed and will  

spread out evenly within it. Unlike those of solids  

and liquids, the volumes of gases are affected quite  

markedly by changes in temperature.

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.