Answer:
6.022 × 10²³ molecules of B₂H₆
Explanation:
The given problem will solve by using Avogadro number.
It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.
The number 6.022 × 10²³ is called Avogadro number.
For example,
18 g of water = 1 mole = 6.022 × 10²³ molecules of water
1.008 g of hydrogen = 1 mole = 6.022 × 10²³ atoms of hydrogen
B₂H₆ molecules:
21.63 g = one mole of B₂H₆= 6.022 × 10²³ molecules of B₂H₆
Must be Selenium (Se). It is two space away from Kr, which means that it needs two extra electron to be like a noble gas, Kr.
Beryllium<span> (Be), </span>magnesium<span> (</span>Mg), calcium (Ca), strontium (Sr<span>), </span>barium<span>(Ba) and radium (Ra). Elements are grouped together because they share similar properties.
Hope i help</span>
Answer:
The amount of heat that is released is -925.2 cal
Explanation:
Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.
Sensible heat is the amount of heat that a body can receive or release without affecting its molecular structure, that is, it does not change the state (solid, liquid, gaseous). In other words, sensible heat is the amount of heat that a body absorbs or releases without any changes in its physical state.
The equation that allows to calculate heat exchanges is:
Q = c * m * ΔT
Where Q is the heat exchanged by a body of mass m, constituted by a substance of specific heat c and where ΔT is the variation in temperature.
In this case:
- c= 1

- m= 25.7 g
- ΔT= Tfinal - Tinitial= 49 °C - 85 °C= -36 °C
Replacing:
Q= 1
*25.7 g* (-36 C)
Solving:
Q= -925.2 cal
<u><em>The amount of heat that is released is -925.2 cal</em></u>
Answer: The given reaction redox reaction not a combustion reaction.
Explanation:
Redox Reaction is defined chemical reaction in which oxidation and reduction takes place simultaneously. In Oxidation addition of oxygen occurs and in reduction addition of hydrogen occurs.

Potassium is getting oxidized by addition of oxygen.
Water us reduced to hydrogen gas by removal of oxygen
Combustion reaction is defined as chemical reaction in which burning of a chemical compound or element takes place in presence of oxygen occurs.
In the given reaction, oxygen molecule is absent which means this reaction is not combustion reaction.
Hence ,the given reaction redox reaction not a combustion reaction.