Answer:
Bohr thought that electrons orbited the nucleus in quantised orbits. ... In Rutherford's model most of the atom's mass is concentrated into the centre (what we now call the nucleus) and electrons surround the positive mass in something like a cloud. Bohr's most significant contribution was the quantisation of the model.
Explanation:
Answer:
0.38dm³ or 38mL
Explanation:
Given parameters:
molarity of HCl = 5.5M
volume of Mg(OH)₂ = 85mL
molarity of Mg(OH)₂ = 1.22M
Unknown:
Volume of HCl solution = ?
Solution:
we have to adopt the mole concept to solve this problem.
Complete reaction equation:
2HCl + Mg(OH)₂ → MgCl₂ + 2H₂O
For a standard acid titrated against a standard base,
aA + bB → cC + dD
A is the acid, B is the base
since number of moles = C x V
C is the molarity
V is the volume
CₐVₐ / CₓVₓ = a / x
a = acid
x = base
85mL to dm³ = 0.085dm³
since the unknown is Vₐ,
let us make it the subject of the expression;
Vₐ = (a/x) x ( CₓVₓ/ Cₐ)
Va = = 0.38dm³
First, we can see that the output is a salt and water which means that the reactants were an acid and a base. Since the given reactant is a base, thus, NH4OH is excluded as it is also a base.
Now, examining the outputs of the reactions, we will find that they are composed mainly of sodium, hydrogen, oxygen and carbon. This excludes H3PO4 as it contains phosphorus.
The last step is to compare between the number of moles of each element in the output with those in the input. The output has 1 sodium mole, 2 carbon moles, 5 hydrogen moles and 3 oxygen moles.
The given input (NaOH) has 1 sodium, 1 oxygen and 1 hydrogen moles. Therefore, the other input (reactant) should have 2 carbon, 4 hydrogen and 2 oxygen moles.
Based on this, the right solution is CH3COOH.
Answer : The pH value of an acid is below 7.
Explanation :
pH : It is defined as the negative logarithm of hydrogen ion or hydronium ion concentration.
Mathematically,
When the pH less than 7 then the solution is acidic and the concentration of hydrogen ion is greater than hydroxide ion.
When the pH more than 7 then the solution is basic and the concentration of hydrogen ion is less than hydroxide ion.
When the pH is equal to 7 then the solution is neutral and the concentration of hydrogen ion is equal to the hydroxide ion.
Hence, the pH value of an acid is below 7.