This question is incomplete, the complete question is;
A buffer solution is prepared by placing 5.86 grams of sodium nitrite and 32.6 mL of a 4.90 M nitrous acid solution into a 500.0 mL volumetric flask and diluting to the calibration mark. If 10.97 mL of a 1.63 M solution of potassium hydroxide is added to the buffer, what is the final pH? The Ka for nitrous acid = 4.6 × 10⁻⁴.
Answer:
the final pH is 3.187
Explanation:
Given the data in the question;
Initial moles of HNO2 = 32.6/1000 × 4.90 = 0.15974 mol
Initial moles of NO2- = mass/molar mass = 5.86/68.995 = 0.0849336 mol
Moles of KOH added = 10.97/1000 × 1.63 = 0.0178811 mol
so
HN02 + KOH → NO2- + H2O
moles of HNO2 = 0.15974 - 0.0178811 = 0.1418589 mol
Moles of NO2- = 0.0849336 + 0.0178811 = 0.1028147 mol
Now,
pH = pka + log( [NO2-]/[HNO2])
pH = -log ka + log( moles of NO2- / moles of HNO2 )
we substitute
pH = -log( 4.6 × 10⁻⁴ ) + log( 0.1028147 / 0.1418589 )
pH = -log( 4.6 × 10⁻⁴ ) + log( 0.724767 )
pH = 3.337242 + (-0.1398 )
pH = 3.187
Therefore, the final pH is 3.187
Answer:
solid
Explanation:
When a solid is melted, for example, thermal energy is what causes the bonds within the solid to break apart.
First let us calculate for the number of moles needed:
moles NaOH = 0.125 M * 0.500 L = 0.0625 mol
The molar mass of NaOH is 40 g/mol, hence the mass is:
mass NaOH = 0.0625 mol * 40 g/mol
<span>mass NaOH = 2.5 grams</span>
Explanation:
Molar mass
The mass present in one mole of a specific species .
The molar mass of a compound , can easily be calculated as the sum of the all the individual atom multiplied by the number of total atoms .
(a) P₄
Molar mass of of the atoms are -
Phosphorous , P = 31 g/mol
Molecular mass of P₄ = ( 4 * 31 ) = 124 g/mol .
(b) H₂O
Molar mass of of the atoms are -
Hydrogen , H = 1 g/mol
oxygen , O = 16 g/mol.
Molecular mass of H₂O = ( 2 * 1 ) + ( 1 * 16 ) = 18 g/mol
(c) Ca(NO₃)₂
Molar mass of of the atoms are -
calcium , Ca = 40 g/mol
nitrogen, N = 14 g/mol
oxygen , O = 16 g/mol.
Molecular mass of Ca(NO₃)₂ = ( 1 * 40 ) + ( 2 * 14 ) + ( 6 * 16 ) = 164 g/mol.
(d)CH₃CO₂H (acetic acid)
Molar mass of of the atoms are -
Carbon , C = 12 g/mol.
oxygen , O = 16 g/mol.
Hydrogen , H = 1 g/mol
Molecular mass of CH₃CO₂H =( 2 * 12 ) + (2 * 16 ) + (4 * 1 ) = 60 g/mol.
(e) C₁₂H₂₂O₁₁ (sucrose, cane sugar).
Molar mass of of the atoms are -
Carbon , C = 12 g/mol.
oxygen , O = 16 g/mol.
Hydrogen , H = 1 g/mol
Molecular mass of C₁₂H₂₂O₁₁ = (12 * 12 ) + ( 22 * 1 ) + ( 11 * 16 ) = 342 g/mol.
