The answer is Na-F. The F has highest electronegativity among these elements. So we need to find the element with smallest electronegativity. And this element is Na.
Answer : The internal energy change is, -506.3 kJ/mol
Explanation :
Formula used :
or,
where,
= change in enthalpy = 
= change in internal energy = ?
= change in moles
Change in moles = Number of moles of product side - Number of moles of reactant side
According to the reaction:
Change in moles = 0 - 2 = -2 mole
That means, value of 
= 0
R = gas constant = 8.314 J/mol.K
T = temperature = 
Now put all the given values in the above formula, we get
Therefore, the internal energy change is -506.3 kJ/mol
Balanced equation:
Ca(OH)2+H2SO4=CaSO4+2 H20<span />
A.
Weldings sparks could start fire on wood.
Lightning can ignite a fire one a tall tree
Open flames can start another fire if made in contact especially with flammable substances
The micromoles of mercury(II) iodide : 0.013 μ moles
<h3>Further explanation</h3>
Given
215.0mL of a 6.0x10⁻⁵mmol/L HgI₂
Required
micromoles of HgI₂
Solution
Molarity(M) = moles of solute per liters of solution
Can be formulated :
M = n : V
n = moles
V = volume of solution
V = 215 mL = 0.215 L
so moles of solution :
n = M x V
n = 6.10 mmol/L x 0.215 L
n = 1.312 . 10⁻⁵ mmol
mmol = 10³ micromol
so 1.312 mmol = 1.312.10⁻⁵ x 10³ = 0.01312 micromoles ⇒ 2 sif fig = 0.013 μ moles
