A lump of chromium (Cr) has a specific heat of 0.448J/g℃. It is heated to a temperature of 89.5℃ and placed into a calorimeter with 75.2 mL of water at 20.5℃. After stirring, the final temperature of the water, Cr metal, and calorimeter is 27.4℃. What is the mass of Cr metal?

Mass of Cr= 78 g

Explanation:

Given data:

Specific heat of Cr = 0.448 j/g.°C

Initial  temperature of Cr lump = 89.5°C

Mass of water = 75.2 mL or 75.2 g

Initial temperature of water = 20.5°C

Final temperature of water = 27.4°C

Mass of Cr = ?

Solution:

when we placed the lump of Cr metal into water heat lost by limp is equal to the heat gain by water.

Specific heat capacity of water is 4.184 j/g.°C

Q = mcΔT

Q = 75.2 g× 4.184 j/g.°C × (27.4°C - 20.5°C)

Q = 2171 J

Heat lost by Cr lump is -2171 J. Now we will calculate the mass of Cr.

Q = mcΔT

-2171 J = m ×0.448 j/g.°C × ( 27.4°C- 89.5°C)

-2171 J = m × -27.821 j/g

m = -2171 J/-27.821 j/g

m = 78 g

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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