Answer: at relatively low temperatures.
Explanation:
According to Gibbs equation;
= Gibb's free energy change
= enthalpy change
T = temperature
= entropy change
A reaction is spontaneous when = Gibb's free energy change is negative.
Thus 
Thus the reaction is spontaneous or is negative only when 
Thus the reaction is spontaneous at relatively low temperatures
C. single replacement. A single replacement is represented by this formula : AB + C = AC + B
In 1 mole of 
, there are 3 moles of ions, 1 mole of Ca^{2+} and 2 mole of 
.
Molar mass of is 110.98 g/mol. Calculating number of moles from given mass as follows:
Thus, number of moles of ions will be 
.
Since, 1 mole of any substance has 
units of that substance where is Avogadro's number.
Thus, 9.38 mol of ions will have 
number of ions.
Therefore, total number of ions in 347 g of is 
.
Answer:
The third one is the correct answer
Explanation:
The population density is 47 people/km^2..
<em>Step 1</em>. Calculate the <em>surface area of Earth</em>.
<em>d</em> = 12 700 km; <em>r</em> = 6350 km
<em>A</em> = 4π<em>r</em>^2 = 4π × (6350 km)^2 = 5.067 × 10^8 km^2
<em>Step 2</em>. Calculate the <em>habitable surface area</em>.
Habitable area = 5.067 × 10^8 km^2 total × (30 km^2 habitable/100 km^2 total) = 1.520 × 10^8 km^2 habitable
<em>Step 3</em>. Calculate the <em>population density
</em>
Population density = 7.1 × 10^9 people/1.520 × 10^8 km^2 = 47 people/km^2
