Answer:
a. 100.0 mL of 0.10 M NH₃ with 100.0 mL of 0.15 M NH₄Cl.
c. 50.0 mL of 0.15 M HF with 20.0 mL of 0.15 M NaOH.
Explanation:
A buffer system is formed in 1 of 2 ways:
- A weak acid and its conjugate base.
- A weak base and its conjugate acid.
Determine whether mixing each pair of the following results in a buffer.
a. 100.0 mL of 0.10 M NH₃ with 100.0 mL of 0.15 M NH₄Cl.
YES. NH₃ is a weak base and NH₄⁺ (from NH₄Cl ) is its conjugate base.
b. 50.0 mL of 0.10 M HCl with 35.0 mL of 0.150 M NaOH.
NO. HCl is a strong acid and NaOH is a strong base.
c. 50.0 mL of 0.15 M HF with 20.0 mL of 0.15 M NaOH.
YES. HF is a weak acid and it reacts with NaOH to form NaF, which contains F⁻ (its conjugate base).
d. 175.0 mL of 0.10 M NH₃ with 150.0 mL of 0.12 M NaOH.
NO. Both are bases.
We are told that there are 1.55 x 10²³ molecules of Cl₂ and we need to calculate the mass of these molecules. We need to do several conversions. The easiest will be to convert the amount of molecules to the number of moles present. To do this, we need to use Avogadro's number which is 6.022 x 10²³ molecules/mole.
1.55 x 10²³ molecules / 6.022 x 10²³ molecules/mole = 0.257 moles Cl₂
Now that we have the moles of Cl₂ present, we can convert this value to a mass of Cl₂ by using the molecular mass of Cl₂. The molecular mass is 70.906 g/mol.
0.257 moles Cl₂ x 70.906 g/mol = 18.3 g Cl₂
Therefore, 1.55 x 10²³ molecules of Cl₂ will have a mass of 18.3 g.
The effusion rate is 1.125 cm/sec for ammonia.
How to find effusion rate ?
Effusion rate (r1) HCl = 43.2 cm/min
Molar mass (m2) NH3 =17.04g/mole
Molar mass (m1) HCl =36.46g/mole
- Substitute the molar masses of the gases into Graham's law and solve for the ratio.
firstly convert 43.2 cm/min into cm/sec i.e., 0.72 cm/sec
Then,
0.72/r2 =√17.04/36.46
r2= 1.125 cm/sec
Hence, the rate of diffusion of ammonia is 1.125 times faster than the rate of diffusion of hydrogen chloride.
learn more about effusion here:
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Answer:
The thermal energy (heat) needed, to raise the temperature of oil of mass 'm' kilogram and specific heat capacity 'c' from 20°C to 180°C is 160·m·c joules
Explanation:
The heat capacity, 'C', of a substance is the heat change, ΔQ, required by a given mass, 'm', of the substance to produce a unit temperature change, ΔT
∴ C = ΔQ/ΔT
ΔQ = C × ΔT
C = m × c
Where;
c = The specific heat capacity
ΔT = The temperature change = T₂ - T₁
∴ ΔQ = m × c × ΔT
Therefore, the thermal energy (heat) needed, ΔQ, to raise the temperature of oil of mass 'm' kilogram and specific heat capacity, 'c' from 20°C to 180°C is given as follows;
ΔQ = m × c × (180° - 20°) = 160° × m·c
ΔQ = 160·m·c joules
