Show the calculation of the final temperature for a 20.8 gram piece of iron heated to 100oc which has been added to a 55.3 gram sample of water at 25.3oc in a coffee cup calorimeter.
c (water) = 4.184 j/g oc; c (fe) = 0.449 j/g oc

Final Temperature = 28.2 oC

Explanation:

Information given;

Mass of Iron = 20.8g

Initial Temperature of Iron = 100C

Mass of water = 55.3g

Initial temperature of water = 25.3 C

The presence of a coffee cup calorimeter hints that there is no heat loss to the surrounding and that the iron and water are at thermal equilibrium.

Thermal equilibrium means that there is no heat transfer going on between the bodies, which simply means that the bodies are at the same temperature.

Hence, both bodies would the same final temperature (T2)

H = M * C * ΔT (For iron)

H = 20.8 * 0.449 * ( 100 - T2)

H = 9.3392 ( 100 - T2)

H = 933.92 - 9.3392T2

H = M * C * ΔT (For water)

H = 55.3 * 4.184 * (T2 - 25.3)

H = 231.3752 (T2 - 25.3)

H = 231.3752T2 - 5853.79

Since they are in thermal equilibrium it means H (Iron) = H (water).

This leads to;

933.92 - 9.3392T2 = 231.3752T2 - 5853.79

231.3752T2 +  9.3392T2  = 5853.79 + 933.92

240.7144 T2 = 6787.71

T2 = 28.2 oC

h let me think

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms