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Keith_Richards [23]
3 years ago
8

Calculate the ph of a 0.021 m nacn solution. [ka(hcn) = 4.9  10–10]

Chemistry
1 answer:
ohaa [14]3 years ago
4 0

<span>Answer is: pH of solution of sodium cyanide is 11.3.
Chemical reaction 1: NaCN(aq) → CN</span>⁻(aq) + Na⁺<span>(aq).
Chemical reaction 2: CN</span>⁻ + H₂O(l) ⇄ HCN(aq) + OH⁻<span>(aq).
c(NaCN) = c(CN</span>⁻<span>) = 0.021 M.
Ka(HCN) =  4.9·10</span>⁻¹⁰<span>.
Kb(CN</span>⁻) = 10⁻¹⁴ ÷ 4.9·10⁻¹⁰ = 2.04·10⁻⁵<span>.
Kb = [HCN] · [OH</span>⁻] / [CN⁻<span>].
[HCN] · [OH</span>⁻<span>] = x.
[CN</span>⁻<span>] = 0.021 M - x..
2.04·10</span>⁻⁵<span> = x² / (0.021 M - x).
Solve quadratic equation: x = [OH</span>⁻<span>] = 0.00198 M.
pOH = -log(0.00198 M) = 2.70.
pH = 14 - 2.70 = 11.3.</span>

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Balance the following half-reaction: (acidic) NO−3(aq) → NO2(aq) Express your answer as a half-reaction. Identify all of the pha
Marrrta [24]

Answer:

2H⁺  + NO₃⁻  + 1e⁻ →  NO₂  + H₂O

Explanation:

NO₃⁻  →  NO₂

In left side, Nitrogen acts with +5 by oxidation number

In right side, the oxidation number is +4

This is a reduction reaction, because the oxidation number has decreased. So the N has gained electrons.

NO₃⁻  + 1e⁻ →  NO₂

In acidic medium, we have to add water, where there are less oxygens to ballance the amount. We have 2 O in left side, and 3 O in right side, so we have to add 1 H₂O on left side.

NO₃⁻  + 1e⁻ →  NO₂  + H₂O

Now that oxygens are ballanced, we have to ballance the hydrogens by adding protons in the opposite side

2H⁺  + NO₃⁻  + 1e⁻ →  NO₂  + H₂O

8 0
3 years ago
Which of the items below could scientists use to date a layer of rock?
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A fossilized fish could be used to identify the date of of the rock layer.
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How many grams of glucose(C6H12O6) are produced by 10.0 grams of water(H2O)?
GaryK [48]

Answer:

16.7 g of glucose

Explanation:

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We can use the chemical equation to determine the theoretical yield.  Based on the equation, for every 6 moles of H₂O, 1 mole of glucose is produced.  The ratio of glucose moles to H₂O moles is 1/6.  

Multiply the moles of H₂O by the ratio to find moles of glucose.  <em>0.0925 mol</em>

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3 0
3 years ago
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Answer:

Single replacement

Explanation:

Chemical equation:

2Al(NO₃)₃ + 3Ca    →    3Ca(NO₃)₂ + 2Al

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It is the reaction in which one elements replace the other element in compound.

AB + C → AC + B

All other options are incorrect because,

Double replacement:

It is the reaction in which two compound exchange their ions and form new compounds.

AB + CD → AD +CB

Synthesis reaction:

It is the reaction in which two or more simple substance react to give one or more complex product.

Decomposition reaction:

It is the reaction in which one reactant is break down into two or more product.

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Combustion reaction:

Reaction in substance react with oxygen and form carbon dioxide and water.

5 0
3 years ago
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