Explanation:
It is often desirable to determine the mass percent of elements in a given compound.
To determine the mass percent of elements:
- Evaluate the formula mass of the compound. This is done by summing the atomic masses of the atoms in the compound together.
- The mass percentage is determined by pacing the mass contribution of each element or group to the formula mass of the compound and multiply by 100.
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The mass of ammonium chloride that must be added is : ( A ) 4.7 g
<u>Given data :</u>
Volume of water ( V ) = 250 mL = 0.25 L
pH of solution = 4.85
Kb = 1.8 * 10⁻⁵
Kw = 10⁻¹⁴
Given that the dissolution of NH₄Cl gives NH₄⁺⁺ and Cl⁻ ions the equation is written as :
NH₄CI + H₂O ⇄ NH₃ + H₃O⁺
where conc of H₃O⁺
[ H₃O⁺ ] = 
and Ka = Kw / Kb
∴ Ka = 5.56 * 10⁻¹⁰
Next step : Determine the concentration of H₃O⁺ in the solution
pH = - log [ H₃O⁺ ] = 4.85
∴ [ H₃O⁺ ] in the solution = 1.14125 * 10⁻⁵
Next step : Determine the concentration of NH₄CI in the solution
C = [ H₃O⁺ ]² / Ka
= ( 1.14125 * 10⁻⁵ )² / 5.56 * 10⁻¹⁰
= 0.359 mol / L
Determine the number of moles of NH₄CI in the solution
n = C . V
= 0.359 mol / L * 0.25 L = 0.08979 mole
Final step : determine the mass of ammonium chloride that must be added to 250 mL
mass = n * molar mass
= 0.08979 * 53.5 g/mol
= 4.80 g ≈ 4.7 grams
Therefore we can conclude that the mass of ammonium chloride that must be added is 4.7 g
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Answer:
1) Length - Meter
2) Mass - Pound
3) Time - Minute
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Answer:
Mass of solid = 189.141 gram
Explanation:
Given:
Total volume = 93 ml
Mass of liquid = 33.7 gram
Density of liquid = 0.865 g/ml
Density of solid = 3.50 g/ml
Find:
Mass of solid = ?
Computation:
Volume of liquid = Mass of liquid / Density of liquid
Volume of liquid = 33.7 / 0.865
Volume of liquid = 38.9595 ml
Volume of solid = Total volume - Volume of liquid
Volume of solid = 93 - 38.9595
Volume of solid = 54.0405 ml
Mass of solid = Volume of solid × Density of solid
Mass of solid = 54.0405 ml × 3.50 g/ml
Mass of solid = 189.141 gram
Answer:
Mechanical Energy to Thermal Energy
When you strike a match, it moves through the air until it rubs against a surface. The rubbing produces the heat required to light the match. This is a transformation from mechanical energy to thermal (heat) energy.
Explanation:
