The answer is: A molecule with a difference in electrical charge between two ends.
Electronegativity (χ) is a property that describes the tendency of an atom to attract a shared pair of electrons.
Atoms with higher electronegativity attracts more electrons towards it, electrons are closer to that atom.
For example fluorine has electronegativity approximately χ = 4 and oxygen χ = 3,5, fluorine attracts electron and he has negative charge and oxygen has positive charge.
Answer:
- <u><em>It is positive when the bonds of the product store more energy than those of the reactants.</em></u>
Explanation:
The <em>standard enthalpy of formation</em>, <em>ΔHf</em>, is defined as the energy required to form 1 mole of a substance from its contituent elements under standard conditions of pressure and temperature.
Then, per defintion, when the elements are already at their standard states, there is not energy involved to form them from that very state; this is, the standard enthalpy of formation of the elements in their standard states is zero.
It is not zero for the compounds in its standard state, because energy should be released or absorbed to form the compounds from their consituent elements. Thus, the first choice is false.
When the bonds of the products store more energy than the those of the reactants, the difference is:
- ΔHf = ΔHf products - ΔHf reactants > 0, meaning that ΔHf is positive. Hence, the second statement is true.
Third is false because forming the compounds may require to use (absorb) or release (produce) energy, which means that ΔHf could be positive or negative.
Fourth statement is false, because the standard state of many elements is not liquid. For example, it is required to supply energy to iron to make it liquid. Thus, the enthalpy of formation of iron in liquid state is not zero.
<span><u><em>Answer:</em></u>
combustion reaction
<u><em>Explanation:</em></u>
In chemistry, a <u>combustion reaction</u> is defined as a reaction between an oxidant and any compound that leads to the production of another compound along with a huge amount of heat.
<u>Now, let's check the reaction given:</u>
C</span>₃H₈<span> + 5 O</span>₂<span> --> 3 CO</span>₂<span> + 4 H</span>₂O<span>
<u>The oxidant</u> is oxygen gas
<u>The compound reacting</u> is propane
<u>The compound produced</u> is carbon dioxide along with water vapor and heat
Therefore, the given reaction is a combustion reaction
Hope this helps :)</span>
