Answer:
C.
Explanation:
Scientific notation is a way of writing small and large numbers. It is a way of expressing a standard form into a scientific form.
<h2>Which of the following reactions is endothermic-</h2><h2>½N2(g) + O2(g) + 8.1 kcal → NO2(g)</h2>
Explanation:
Chemical reaction
When two or more substances react and form some new substance it is called as chemical reaction .
A + B --> C + D
(reactants ) (products )
When ever chemical reaction occurs following changes can occur :
- Change in colour
- Ppt formation
- energy changes
- Change in state
- Evolution of gas etc
On the basis of energy changes : reactions are of two types :
Endothermic
Exothermic
Endothermic reaction
A reaction in which heat is absorbed .
Example :½N2(g) + O2(g) + 8.1 kcal → NO2(g)
Exothermic reaction
A reaction in which heat is released .
For example : H2(g) + ½O2(g) → H2O(g), ΔH = -57.82 kcal
½N2(g) + 3/2H2(g) → NH3(g) + 11.0 kcal
C(diamond) + O2(g) → CO2, ΔH = -94.50 kcal
Answer:
0.053 M is the concentration of X after 196 seconds.
Explanation:
Initial concentration of the X = ![[A_o]=1.0 M](https://tex.z-dn.net/?f=%5BA_o%5D%3D1.0%20M)
Time taken by the sample, t = 196 s
Final concentration of the X after t = [A] =?
Rate constant of the reaction = k = 
Formula used :
![[A]=[A_o]\times e^{-kt}](https://tex.z-dn.net/?f=%5BA%5D%3D%5BA_o%5D%5Ctimes%20e%5E%7B-kt%7D)
where,
Now put all the given values in this formula, we get
![[A]=[1.0M]\times e^{-1.50\times 10^{-2} s^{-1}\times 196 s}](https://tex.z-dn.net/?f=%5BA%5D%3D%5B1.0M%5D%5Ctimes%20e%5E%7B-1.50%5Ctimes%2010%5E%7B-2%7D%20s%5E%7B-1%7D%5Ctimes%20196%20s%7D)
![[A]=0.053 M](https://tex.z-dn.net/?f=%5BA%5D%3D0.053%20M)
0.053 M is the concentration of X after 196 seconds.
Answer:
5. An element's mass number tells the number of protons in its nucleus.
Atomic
6. Negatively charged particles in an atom are called electrons.
True
7. The cloud model of the atom describes the location of electrons as specific orbits around the nucleus.
Bohr
8. Atoms with the same number of protons but different numbers of neutrons are called isomers.
Isotopes
9. The sum of the protons and neutrons in an atom is called the atomic number.
Mass
10. An object that helps explain ideas about the natural world is called a model.
True
11. Mendeleev arranged his periodic table in order of increasing atomic number.
Mass
12. The rows in the periodic table are called periods.
True
13. Moving across the periodic table from left to right, one finds, in order, metals, then gases, then nonmetals.
Metalloids
14. Another name for a period is a family.
Group
15. On the periodic table, elements in the same column have similar properties.
True
Explanation:
