Answer : The standard enthalpy of formation of ethylene is, 51.8 kJ/mole
Explanation :
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
The formation reaction of 
will be,
The intermediate balanced chemical reaction will be,
(1) 
(2) 
(3) 
Now we will reverse the reaction 1, multiply reaction 2 and 3 by 2 then adding all the equations, we get :
(1) 
(2) 
(3) 
The expression for enthalpy of formation of will be,
Therefore, the standard enthalpy of formation of ethylene is, 51.8 kJ/mole
It is an exothermic reaction
Answer:
2.11 x 10²⁴ molecules.
Explanation:
- <em>It is known that every 1.0 mole of a molecule contains Avogadro's number of molecules (NA = 6.022 x 10²³).</em>
<em><u>Using cross multiplication:</u></em>
1.0 mole of H₂O contains → 6.022 x 10²³ molecules.
3.5 mole of H₂O contains → ??? molecules.
∴ 3.5 mole of H₂O contain = (3.5 mol)(6.022 x 10²³) = 2.11 x 10²⁴ molecules.
<h3>
Answer:</h3>
0.012 dekameters (dkm)
<h3>
Explanation:</h3>
<u>We are given;</u>
Required to identify the measurements that is not equivalent to 120 cm.
- Centimeters are units that are used to measure length together with other units such as kilometers(km), meters (m), millimeters (mm), dekameters (dkm), etc.
- These units can be inter-converted to one another using suitable conversion factors.
- To do this, we are going to have a table showing the suitable conversion factor from one unit to another.
Kilometer (km)
10
Decimeter (Dm)
10
Hectometer (Hm)\
10
Meter (m)
10
Dekameter (dkm)
10
Centimeter (cm)
10
Millimeter (mm)
Therefore;
To convert cm to km
Conversion factor is 10^5 cm/km
Thus;
120 cm = 120 cm ÷ 10^5 cm/km
= 0.0012 km
To convert cm to dkm
Conversion factor is 10 cm/dkm
Therefore,
120 cm = 120 cm ÷ 10 cm/dkm
= 12 dkm
To convert cm to m
The suitable conversion factor is 10^2 cm/m
Thus,
120 cm = 120 cm ÷ 10^2 cm/m
= 1.2 m
To convert cm to mm
Suitable conversion factor is 10 mm/cm
Therefore;
120 cm = 120 cm × 10 mm/cm
= 1200 mm
Therefore, the measurement that is not equal to 120 cm is 0.012 dkm
The metal is sodium, Na.
<u>Explanation:</u>
K₂O is an ionic compound in which K is in the oxidation state of +1 and it belongs to group 1.
Group 1 elements also form oxides with the metals with the general formula M₂O and M being Na, K, Li and so on.
Metals Like sodium and Potassium are so brittle in nature and also their oxides.
So the other metal that form metal oxide which is brittle as well as ionic in nature, and so the metal oxide is Na₂O.
So the metal is sodium, Na.
