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Phoenix [80]
2 years ago
7

I need help with the last two questions please help quickly!!

Chemistry
1 answer:
Talja [164]2 years ago
6 0

Not sure about the last one, but I think the percent composition of zinc would be ~ 42.8232

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What is the [h​3​o​+​] in a solution that consists of 1.0 m nh​3​ and 2.5 m nh​4​cl? [k​b​ (nh​3​) = 1.8 ×10​-5​]a) 1.1 × 10​-5​
Archy [21]

Answer:

[H₃O⁺] = 1.4 × 10⁻⁹ M.

Explanation:

NH₄Cl is a salt that dissolves well in water. The 2.5 M NH₄Cl will give an initial NH₄⁺ concentration of 2.5 M.

NH₃ is a weak base. It combines with water to produce NH₄⁺ and OH⁻. The opposite process can also take place. NH₄⁺ combines with OH⁻ to produce NH₃ and H₂O. The final H₃O⁺ concentration can be found from the OH⁻ concentration. What will be the final OH⁻ concentration?

Let the increase in OH⁻ concentration be x. The initial OH⁻ concentration at room temperature is 10⁻⁷ M.

Construct a RICE table for the equilibrium between NH₃ and NH₄⁺:

\begin{array}{c|ccccccc}\text{R}&\text{NH}_3 &+&\text{H}_2\text{O}&\rightleftharpoons &{\text{NH}_4}^{+}&+&\text{OH}^{-}\\\text{I}&1.0&&&&2.5&&1.0\times 10^{-7}\\\text{C}& -x &&&& +x &&+x\\\text{E} &1.0 - x &&&&2.5+x&&1.0\times 10^{-7}+x\end{array}.

The \text{K}_b value for ammonia is small. The value of x will be so small that at equilibrium, 1.0 - x \approx 1.0 and 2.5- x \approx 2.5.

\displaystyle \text{K}_b = \frac{[{\text{NH}_4}^{+}]\cdot [{\text{OH}}^{-}]}{[\text{NH}_3]} \approx \frac{2.5\;(x + 1.0\times 10^{-7})}{1.0}.

\displaystyle \frac{2.5\;(x + 1.0\times 10^{-7})}{1.0} = 1.8\times 10^{-5}.

\displaystyle [\text{OH}^{-}] = x+1.0\times 10^{-7} = 1.8\times 10^{-5} /\left(\frac{2.5}{1.0}\right) = 7.2\times 10^{-6}\;\text{mol}\cdot\text{L}^{-}.

Again, \text{K}_w = 1.0\times 10^{-14} at room temperature.

\displaystyle [\text{H}_3\text{O}^{+}] = \frac{\text{K}_w}{[\text{OH}^{-}]}=\frac{1.0\times 10^{-14}}{7.2\times 10^{-6}} = 1.4\times 10^{-9} \;\text{mol}\cdot\text{L}^{-1}

7 0
3 years ago
How many moles are in 25grams of na2so4
Sphinxa [80]
Moles= grams of compound/molar mass of compound ??
5 0
3 years ago
Read 2 more answers
Motion is... Question 1 options: A change in speed over a certain amount of time. A change in position over a certain amount of
Pie
A change in position over a cetain time
6 0
3 years ago
ASAP
sammy [17]

The answer is C.

The vast difference in electronegativity of the oxygen and hydrogen in water, the O-H bond is polar.

8 0
2 years ago
A calorimeter contains 251 g of water at 24.3 C.The temperature of the water decreases to 18.5 C when 12.5 g of potassium nitrat
vova2212 [387]

Answer:

Endothermic  

Explanation:

The temperature of the water decreased.

The water lost heat.

The heat must have gone into getting the KNO₃ into solution.

So, the dissolving of KNO₃ in water is endothermic.

8 0
3 years ago
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