Answer:
3.0 x 10²⁴molecules
Explanation:
Given parameters:
Number of moles of compound = 5moles
Unknown:
Number of molecules = ?
Solution:
A mole is substance that contains the Avogadro's number of particles;
1 mole = 6.02 x 10²³ molecules
5 moles of the compound will give 5 x 6.02 x 10²³ molecules
= 3.0 x 10²⁴molecules
First we calculate the concentration of HCl:
Moles = mass / Mr
= 25 / 36.5
= 0.685 mol
Concentration = 0.685/1.5 = 0.457 mol / dm³
For a strong monoprotic acid, the concentration of hydrogen ions is equal to the acid concentration.
pH = -log[H+]
pH = -log(0.457)
= 0.34
- Standard reduction potential of Ag/Ag⁺ is 0.80 v and that of Cu⁺²(aq)/Cu⁰ is +0.34 V.
- The couple with a greater value of standard reduction potential will oxidize the reduced form of the other couple.
Ag⁺ will be reduced to Ag(s) and Cu⁰ will be oxidized to Cu²⁺
Anode reaction: Cu⁰(s) → Cu²⁺ + 2 e⁻ E⁰ = +0.34 V
Cathode reaction: Ag⁺(aq) + e → Ag(s) E⁰ = +0.80 V
Cell reaction: Cu⁰(s) + 2 Ag⁺(aq) → Cu⁺²(aq) + 2 Ag⁰(s)
E⁰ cell = E⁰ cathode + E⁰ anode
= 0.80 + (-0.34) = + 0.46 V
<u>Given:</u>
Calculated density values-
Aluminum = 2.7 g/cm3
Copper = 9.0 g/cm3
Iron = 7.9 g/cm3
Titanium = 4.8 g/cm3
Unknown sample mass = 9.5 g
Sample volume = 2.1 cm3
<u>To determine:</u>
The identity of the unknown sample
<u>Explanation:</u>
'Density' is a physical parameter which can be used to identify the nature of the unknown substance.
Density = Mass/Volume
For the unknown sample
Density = 9.5 g/2.1 cm3 = 4.52 g/cm3
This matches closely with the calculated density of titanium
Ans: The unknown substance is made of titanium
Answer:
by moving between defined energy levels
