Answer:
m = 31.284 grams
Explanation:
Given that,
The dimension of a magnesium block is 2.00 cm x 3.00 cm x 3.00 cm.
The density of magnesium is, d = 1.738 g/cm³
We need to find the mass of the magnesium block. We know that the density of an object is given by its mass per unit its volume. So,

So, the mass of the block is 31.284 grams.
The identity of the metal is copper.
<h3>What is specific heat?</h3>
The amount of energy needed to raise the temperature of one gram of a substance by one degree Celsius.
Using the formula of specific heat
H = mcdT
Where, H = Heat absorbed
m = mass of the metal
c = specific heat capacity of the metal
dT = temperature change
Putting the values in the equation
20 J = 0.0052 Kg × c × ( 40.0°C - 30.0°C)
c = 20 J/0.0052 Kg × ( 40.0°C - 30.0°C)
c = 385 JKg-1°C-1
Thus, the metal is copper.
Learn more about specific heat
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The equilibrium constant, Kc=0.026
<h3>Further explanation</h3>
Given
1.72 moles of NOCI
1.16 moles of NOCI remained
2.50 L reaction chamber
Reaction
2NOCI(g) = 2NO(g) + Cl2(g).
Required
the equilibrium constant, Kc
Solution
ICE method
2NOCI(g) = 2NO(g) + Cl2(g).
I 1.72
C 0.56 0.56 0.28
E 1.16 0.56 0.28
Molarity at equilibrium :
NOCl :

NO :

Cl2 :

![\tt Kc=\dfrac{[NO]^2[Cl_2]}{[NOCl]^2}\\\\Kc=\dfrac{0.224^2\times 0.112}{0.464^2}=0.026](https://tex.z-dn.net/?f=%5Ctt%20Kc%3D%5Cdfrac%7B%5BNO%5D%5E2%5BCl_2%5D%7D%7B%5BNOCl%5D%5E2%7D%5C%5C%5C%5CKc%3D%5Cdfrac%7B0.224%5E2%5Ctimes%200.112%7D%7B0.464%5E2%7D%3D0.026)