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olga55 [171]
3 years ago
13

Which best represents a physical change?

Chemistry
1 answer:
Zinaida [17]3 years ago
4 0

Answer:

The answer I would go with is A formation of a new substance.

Explanation:

This is because physical change includes changes of state. Some could be changing from a liquid to gas or solid to gas. B is not even an answer that should be considered because it doesn't fit into the category. C and D represents some of the examples of the process of physical change. Like boiling, bubbling, melting, or freezing. So the best would be A.

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Shalnov [3]
Ok pick the letter b that’s what I think it is
7 0
4 years ago
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Will the ph of a solution of nh4cn be &gt;7, &lt;7, or =7?
never [62]
PH of a solution will be <span>higher than 7
</span>
Ammonium cyanide is a salt formed by hydrogen cyanide and ammonia. Ammonia is a weak base and hydrogen cyanide is a weak acid. 
NH₄CN + H₂O ⇒ NH₃ + HCN 

NH₄⁺ + H₂O -----> H₃O⁺ + NH₃

CN⁻ + H₂O -----> HCN + OH⁻ 

Although both compounds are weak electrolytes, NH₃ is somewhat stronger base than HCN is a strong acid, so the solution reacts alkaline. We can prove this using Ka and Kb values:

Ka(HCN) = 4.9 x × 10⁻¹⁰

Kb(NH₃) = 1.8 × 10⁻⁵<span>
Kw= </span>1.0 × 10⁻¹⁴

Let's first calculate Ka for NH₄⁺: 
Ka(NH₄⁺) x Kb(NH₃<span>) = pKw

</span>Ka(NH₄⁺) = Kw/Kb(NH₃) = 5.6 x 10⁻¹⁰

Then, Kb for CN⁻:

Kb(CN⁻) x Ka(HCN) = pKw

Kb(CN⁻) = Kw/Ka(HCN) = 2 x 10⁻⁵

 
From this, we can see that the acid constant NH4⁺ is much lower than the base constant of CN⁻, which will say that the solution of NH₄CN will react slightly alkaline because of the higher presence of hydroxyl ions in solution.


7 0
4 years ago
What is the mass of 0.28 mol of iron
maria [59]
Mass = number of mol x molar mass
Mass = 0.28mol x 55.8g/mol
Mass = 15.624g
5 0
3 years ago
Read 2 more answers
Please help me with this question!! read the photo
pishuonlain [190]

There are 1.92 × 10^23 atoms Mo in the cylinder.

<em>Step 1</em>. Calculate the <em>mass of the cylinder </em>

Mass = 22.0 mL × (8.20 g/1 mL) = 180.4 g

<em>Step 2</em>. Calculate the<em> mass of Mo </em>

Mass of Mo = 180.4 g alloy × (17.0 g Mo/100 g alloy) = 30.67 g Mo

<em>Step 3</em>. Convert <em>grams of Mo</em> to <em>moles of Mo </em>

Moles of Mo = 30.67 g Mo × (1 mol Mo/95.95 g Mo) = 0.3196 mol Mo

<em>Step 4</em>. Convert <em>moles of M</em>o to <em>atoms of Mo </em>

Atoms of Mo = 0.3196 mol Mo × (6.022 × 10^2<em>3</em> atoms Mo)/(1 mol Mo)

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7 0
3 years ago
3. What mass of copper could be deposited from a copper(II) Sulphate solution using a current of 5.0 A over 100 seconds? ( F =96
arsen [322]

Mass of copper : 0.165 g

<h3>Further explanation</h3>

Given

5.0 A over 100 seconds

Required

Mass of copper

Solution

Faraday's law:

<em>The mass of the substance formed at each electrode is proportional to the electric current flowing in the electrolysis</em>

<em />\tt W=\dfrac{e.i.t}{96500}<em />

e = Ar / valence = eqivalent weight

i = current

t = time

W = weight

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Cu ----> Cu²⁺ + 2e

e = Ar/2

= 63,5/2 = 31,75

\tt W=\dfrac{31.75\times 5\times 100}{96500}=0.165~g

8 0
3 years ago
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