Answer:
An ion channel, more specifically a calcium channel.
Explanation:
The electrical activity of the cells is regulated by ion channels. Calcium channels, also referred as the voltage-gated calcium channels constitute one group of a superfamily of ion channels. A change in voltage across the membrane or small molecules triggers calcium channels to open, allowing calcium to flow into the cell. Inside the cell, calcium acts as a second messenger, it binds to calcium sensitive proteins to induce different responses and support several functions such as muscle contraction, hormone and neurotransmitter secretion, gene regulation, activation of other ion channels, control of action potentials, cell survival, etc.
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 reaction of a metal with oxygen to form rust is called as redox reaction.
Explanation:
The process during which the surface of metal reacts with the oxygen ions present in air, it has tendency to get oxidized that is formation of an oxide layer on the surface of the metal. Generally, it occurs when metals like iron comes in contact with moisture or water. So the oxygen in moisture reacts with iron giving its electron and getting oxidized and reducing the surface of metal by forming metal oxide. So the complete process of formation of rust is termed as redox reaction. As here both oxidation and reduction is taking place.
The tendency of a moving object to continue moving in a straight line or a stationary object to remain in place is called inertia.
Answer: C) or the third option.
