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Reil [10]
3 years ago
10

Which of the following reactions have a positive ΔSrxn? Check all that apply.

Chemistry
1 answer:
PolarNik [594]3 years ago
6 0

Answer:

The reactions that have a <em>positive ΔS rxn </em>are the first and the fourth choices:

  • <em>2A(g) + B(s) → 3C(g)</em>

  • <em>2A(g) + 2B(g) → 5C(g)</em>

Explanation:

<em>ΔS rxn </em>is the change of entropy of the chemical reaction.

ΔS rxn = S after reaction - S before reaction.

Therefore, a positive ΔS rxn  means that the entropy after the reaction is greater than the entropy before the reaction.

You may use some assumptions to predict whether a reaction will lead an increase or decrease of the entropy.

First, assume that all the non-shown conditions, such as temperature and pressure, are constant.

Under that assumption, and from the meaning of entropy as a measure of the disorder or randomness of a system you can predict the sign of the change of entropy.

  • <em><u>2A(g) + B(s) → 3C(g)</u></em>

        1)  The solid compounds, B(s) in this case, are very ordered and so they have low entropy.

        2) Gas molecules are highly disordered (scattered), and the greater the number of molecules of the gas the larger the entropy, S).

Hence, since the product side shows 3 gas molecules and the reactant side shows 2 gas molecules and 1 solid molecule, you predict that the products have a larger entropy than the reactants, meaning an increase in entropy: <em>ΔS rxn is positive.</em>

  • <em><u>2A(g) + B(g) → C(g)</u></em>

Using the same reasoning, 3 gas molecules in the  reactant side have more entropy than 1 molecule in the product side, and so the reaction leads to a decrease in the entropy: ΔS rxn is negative

  • <u><em>A(g) + B(g) → C(g)</em></u>

Again, 2 gas molecules in the  reactant side have more entropy than 1 molecule in the product side, and so the reaction leads to a decrease in the entropy: ΔS rxn is negative

  • <u><em>2A(g) + 2B(g) → 5C(g)</em></u>

With the same reasoing, 5 molecules in the product side, lets you predict that will have more entropy than 4 molecules in the reactant side, and, the entropy will increase: <em>ΔS rxn is positive.</em>

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Arte-miy333 [17]

The volume of the stock solution needed is 213.88 mL to get new concentration.

<h3>What is molarity?</h3>

Molarity (M) is the amount of a substance in a certain volume of solution. Molarity is defined as the moles of a solute per litres of a solution.

Determination of the volume of stock solution.

Volume of diluted solution (V₂) =550 mL

Molarity of diluted solution (M₂) =0.70 M

Molarity of stock solution (M₁) = 1.8 M

Volume of stock solution needed (V₁) =?

M₁V₁ = M₂V₂

1.8 M  × V₁ = 0.70 M × 550 mL

V₁ = 213.88 mL

Thus, the volume of the stock solution needed is 213.88 mL.

Learn more about the molarity here:

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Answer:

Glycogen. Cellulose. Amylose. Cellulose. Amylopetin and Glycogen. Amylopetin and Cellulose.

Explanation:

Glycogen is the form that glucose is stored in human body.

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Amylose is the polysaccharide linked mainly by the the bonds of \alpha 1,4 glycosidic.

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Amylopetin and Glycogen are branched polysaccharides linked by the bonds of \alpha 1,4 glycosidic and \alpha 1,6 glycosidic.

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Step 1: calculate amount of substance of sodium and chlorine.
n(Na) = m(Na)÷M(Na) = 46g ÷ 23 g/mol = 2 mol.
n(Cl₂) = m(Cl₂)÷M(Cl₂) = 71g ÷ 71 g/mol = 1 mol.
Step 2: calculate amount of substance and mass of sodium-chloride.
Because both sodium and chlorine react completely, we can use both n to compare with n of NaCl.
n(Na) : n(NaCl) = 2:2, 2 mol : n(NaCl) = 2:2
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