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4 years ago

How did the work of louis pasteur help modern day medicine?

1 answer:

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Pasteur showed that airborne microbes were the cause of disease. Pasteur built on the work of Edward Jenner and helped to develop more vaccines Pasteur’s career showed how conservative the medical establishment was at the time.

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What do you call each of the following changes of state:

Alinara [238K]

a. Solid to liquid - melting process

b. Liquid to gas - evaporation process

c. Gas to solid - deposition process

d. Solid to gas - sublimation process

e. Liquid to solid - solidification process

f. Gas to liquid - condensation process

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3 years ago

Support heat has convenient

andreyandreev [35.5K]

Hgdhisybdjxfhdjgf fhcgh ftgi

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3 years ago

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

PolarNik [594]

Answer:

The reactions that have a positive ΔS rxn are the first and the fourth choices:

2A(g) + B(s) → 3C(g)

2A(g) + 2B(g) → 5C(g)

Explanation:

ΔS rxn 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.

2A(g) + B(s) → 3C(g)

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: ΔS rxn is positive.

2A(g) + B(g) → C(g)

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

A(g) + B(g) → C(g)

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

2A(g) + 2B(g) → 5C(g)

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: ΔS rxn is positive.

6 0

4 years ago

A certain element has only two naturally occurring isotopes: one with 18 neutrons and the other with 20 neutrons. The element fo

melamori03 [73]

Answer:

[Cl-18]⁻ & [Cl-20]⁻

Explanation:

By definition isotopes are elements with the same number of protons by different number of neutrons. Elements X-18 & X-20 have 17 protons and represent Chlorine isotopes Cl-18 & Cl-20 each with 17 protons and 18 electrons to give the isotopes a -1 oxidation state. Both isotope of chlorine have 7 electron in its valence shell and 10 electrons in its core structure. Gaining 1 electron fills the valence octet and establishes a -1 oxidation state.

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3 years ago

What is the first step of a ladybug during the growth and development process

Sunny_sXe [5.5K]

Answer:

Damian here! (ﾉ◕ヮ◕)ﾉ*:･ﾟ✧

The newly hatched larva is in its first instar, a developmental stage that occurs between molts. It feeds until it grows too big for its cuticle, or soft shell, and then it molts. After molting, the larva is in the second instar. Ladybug larvae usually molt through four instars, or larval stages, before preparing to pupate.

Explanation:

hope this helps? :))

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3 years ago