Answer:
0.12 M hydrofluoric acid + 0.17 M potassium fluoride
Explanation:
To make a buffer, you must to have an aqueous mixture of a weak acid and its conjugate base or vice versa.
Knowing that:
0.32 M calcium chloride + 0.27 M sodium chloride: <em>is not a good buffer system </em>because CaCl₂ and NaCl are both salts.
0.35 M ammonia + 0.36 M calcium hydroxide <em>is not a good buffer system </em>because ammonia is a weak base but calcium hydroxide is a strong base
0.19 M barium hydroxide + 0.28 M barium chloride <em>is not a good buffer system </em>because Ba(OH)₂ is a strong base.
0.12 M hydrofluoric acid + 0.17 M potassium fluoride <em>is a good buffer system </em>because HF is a weak acid and KF (F⁻ in aqueous medium), is its conjugate base
0.20 M hydrobromic acid + 0.22 M sodium bromide <em>is not a good buffer system </em>because HBr is a strong acid.
What does the lab say because then i can help :)
Isobaric transition, first law: <span>H=ΔU+w</span>
for a gas expansion: <span>w=<span>P<span>ext</span></span>∗ΔV</span>
to convert to joules, you need the gas constants.
R = 0.08206 L atm/mol*K, R=8.314 J/mol*K
<span>w=<span>P<span>ext</span></span>∗ΔV∗<span><span>8.314 J/mol∗K</span><span>0.08206 L atm/mol∗K</span></span></span>
<span>ΔU=ΔH−[<span>P<span>ext</span></span>∗ΔV∗<span><span>8.314 J/mol∗K</span><span>0.08206 L atm/mol∗K</span></span>]</span>
<span>ΔU=−75000 J−[(43.0atm)∗(2−5)L∗<span><span>8.314 J</span><span>0.08206 L atm</span></span>]</span>
Then you need to convert to kJ.
by the way U=E, internal energy.
Answer: 1. 
2. 3 moles of 
: 2 moles of 
3. 0.33 moles of : 0.92 moles of
4. is the limiting reagent and is the excess reagent.
5. Theoretical yield of 
is 29.3 g
Explanation:
To calculate the moles :
The balanced chemical equation is:
According to stoichiometry :
3 moles of require = 2 moles of
Thus 0.33 moles of will require=
of
Thus is the limiting reagent as it limits the formation of product and is the excess reagent.
As 3 moles of give = 2 moles of
Thus 0.33 moles of give = of
Theoretical yield of 
Thus 29.3 g of aluminium chloride is formed.
By the second law of thermodynamics:
Heat can not spontaneously flow from cold regions to hot regions without external work being performed on a system.
Heat transfer is the passage of thermal energy from a hot ( t B = 80° C ) to a colder body ( t A = 40° C ).
Answer: B ) Heat flows from object B to object A.
