A hot lump of 39.9 g of iron at an initial temperature of 78.1 °C is placed in 50.0 mL H 2 O initially at 25.0 °C and allowed to reach thermal equilibrium. What is the final temperature of the iron and water, given that the specific heat of iron is 0.449 J/(g⋅°C)? Assume no heat is lost to surroundings.

Answer : The final temperature of the mixture is

Explanation :

In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.

where,

= specific heat of iron =

= specific heat of water =

= mass of iron = 39.9 g

= mass of water  =

= final temperature of mixture = ?

= initial temperature of iron =

= initial temperature of water =

Now put all the given values in the above formula, we get

Therefore, the final temperature of the mixture is

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

the positions which points up in upward carbon and down in downward carbon are axial

and vice versa holds true for equatorial positions

so the correct answer with labelled diagram will be