Answer:
the average answer in maybe 60
If 10 g of NaOH is diluted to 500 ml with water then the concentration expressed in percent is 0.5 mol/L .
Calculation ,
Given mass in gram = 10 g
Number of moles = given mass /molar mass = 10 g / 40 g/mol = 0.25mole
Given volume in ml = 500 ml
Given volume in liter = 0.5 L
Putting the value of mass and volume in equation i we get concentration expressed in percent .
C = number of moles ×100/ volume in liter = 0.25mole ×100/ 0.5 L
C = 0.5 mol/L
Concentration of solution in terms of percentage can be expressed in two ways
1) percentage by mass
2) percentage by volume
Hence, for liquid solutions, concentration is expressed in terms of percentage by volume.
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Answer:
Explanation:
Given parameters:
pH = 3.50
Unknown:
concentration of [H₃0⁺] = ?
concentration of [OH⁻] = ?
Solution:
In order to find the unknown, we use some simple expressions which best explains the pH scale and the equilibrium systems of aqueous solutions.
pH = -log₁₀[H₃O⁺]
[H₃O⁺] = inverse log₁₀ (-pH) =
= 
[H₃O⁺] = 3.2 x 10⁻⁴moldm⁻³
For the [OH⁻]:
we use : pOH = -log₁₀ [OH⁻]
Recall: pOH + pH = 14
pOH = 14 - pH = 14 - 3.5 = 10.5
Now we plug the value of pOH into pOH = -log₁₀ [OH⁻]
[OH⁻] = 
[OH⁻] =
= 3.2 x 10⁻¹¹moldm⁻³
The solution is acidic as the concentration of H₃0⁺ is more than that of the OH⁻ ions.
3.37 x 10¹⁰ molecules
Explanation:
Given parameters:
Volume of water = 1pL = 1 x 10⁻¹²L
Density of water = 1.00g/mL = 1000g/L
Unknown:
Number of water molecules = ?
Solution:
To solve this problem, we first find the mass of the water molecule in the inkjet.
Mass of water = density of water x volume of water
Then, the number of molecules can be determined using the expression below:
number of moles = 
Number of molecules = number of moles x 6.02 x 10²³
Solving:
Mass of water = 1 x 10⁻¹² x 1000 = 1 x 10⁻⁹g
Number of moles:
Molar mass of H₂O = 2 + 16 = 18g/mol
Number of moles =
= 5.6 x 10⁻¹⁴moles
Number of molecules = 5.6 x 10⁻¹⁴ x 6.02 x 10²³ = 33.7 x 10⁹
= 3.37 x 10¹⁰ molecules
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