The first one
............
Answer:
4.48 grams of potassium hydroxide that the chemist must be weighing out.
Explanation:
The pH of the KOH solution = 13
pH + pOH = 14
pOH = 14 - pH = 14 - 13 = 1
![pOH=-\log[OH^-]](https://tex.z-dn.net/?f=pOH%3D-%5Clog%5BOH%5E-%5D)
![1=-\log[OH^-]](https://tex.z-dn.net/?f=1%3D-%5Clog%5BOH%5E-%5D)
![[OH^-]=0.1 M](https://tex.z-dn.net/?f=%5BOH%5E-%5D%3D0.1%20M)

1 mole of hydroxide ions are obtained from 1 mole of KOH. Then 0.1 mole of hydroxide ions will be obtained from :
of KOH
![[Molarity]=\frac{\text{Moles of solute}}{\text{Volume of solution(L)}}](https://tex.z-dn.net/?f=%5BMolarity%5D%3D%5Cfrac%7B%5Ctext%7BMoles%20of%20solute%7D%7D%7B%5Ctext%7BVolume%20of%20solution%28L%29%7D%7D)
Volume of KOH solution = 800 mL = 0.800 L ( 1 mL = 0.001 L)

Moles of KOH = 0.1 M × 0.800 L = 0.08 mol
Mass of 0.08 moles of KOH :
0.08 mol × 56 g/mol = 4.48 g
4.48 grams of potassium hydroxide that the chemist must be weighing out.
Endothermic reactions are reactions that proceed by the absorption of heat (energy) while exothermic reactions involve a release of energy.
a) Formation of frost on a car window in winter is an exothermic process as heat is liberated when liquid water freezes to form crystals
b) Formation of water condensate on a glass of ice water is an endothermic reaction since heat is absorbed by the cold water from the glass container thereby cooling it.
c) A decrease in the temperature as ammonium nitrate is added to water is an endothermic reaction
Answer:
elements have the same number of valence electrons and similar chemical properties.
Explanation:
they have the same number