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.
The force of an object due mass and gravity.it can also be defined as the force exerted by gravity on a body
Answer : The protons and neutrons subatomic particles will be located at Z.
Explanation :
In the model of an atom, there are three subatomic particles. Protons, neutrons and electrons are the subatomic particles.
The protons and the neutrons subatomic particles are located inside the nucleus and the electrons subatomic particle are located around or outside the nucleus.
The protons are positively charged, electrons are negatively charged and neutrons are neutral that means it has no charge.
In the given dartboard, Z is the nucleus in which the protons and neutrons subatomic particles are present and x, w & y are the electrons because they are located around the nucleus.
Hence, the protons and neutrons subatomic particles will be located at Z.
Answer:
d.
Explanation:
They can be spread through contaminated surfaces.
Answer:
because the fossils are beutifule
Explanation:
because the fossils are rare in the world
