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3 years ago

The main factor that influences the direction of any periodic trend across a period is ______.

Chemistry

1 answer:

aalyn [17]3 years ago

3 0

Answer:

The correct option is B

Explanation:

The number of valence electron(s) increases across the period and thus influences the direction of periodic trend of electronegativity, electron affinity and ionization energy across the period. Thus, making option B the answer.

It should be noted that option A is wrong because elements in the same period generally have the same number of electron shells and thus the distance of this shells from the nucleus remains the same throughout the same period and thus option C is also wrong. Option D is wrong because the periodic trends have to do with chemical reactions which actually involves electrons and not protons.

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How many variables are there in science

Sedaia [141]

There are three variables independent, dependent ,and controlled

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3 years ago

What is the difference between parent material

Kazeer [188]

Answer:

Parent material is the geologic material from which soil horizons form. Many soils have more than one parent material, for example loess over till. ... Every soil horizon has a parent material, but the same parent material usually appears different in different horizons because soil formation processes have altered it.

Explanation:

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3 years ago

In the reaction C + O2 → CO2, 18 g of carbon react with oxygen to produce 72 g of carbon dioxide. What mass of oxygen would be n

artcher [175]

Stoichiomety:

1 moles of C + 1 mol of O2 = 1 mol of CO2

multiply each # of moles times the atomic molar mass of the compund to find the relation is weights

Atomic or molar weights:

C: 12 g/mol
O2: 2 * 16 g/mol = 32 g/mol
CO2 = 12 g/mol + 2* 16 g/mol = 44 g/mol

Stoichiometry:

12 g of C react with 32 g of O2 to produce 44 g of CO2

Then 18 g of C will react with: 18 * 32/ 12 g of Oxygen = 48 g of Oxygen

And the result will be 12 g of C + 48 g of O2 = 60 g of CO2.

You cannot obtain 72 g of CO2 from 18 g of C.

May be they just pretended that you use the law of consrvation of mass and say that you need 72 g - 18g = 54 g. But it violates the proportion of C and O2 in the CO2 and is not possible.

3 0

4 years ago

Read 2 more answers

Rank these acids according to their expected pKa values.

givi [52]

Answer:

According to their expected pKa values, the order of those acids should be:

1- Cl2CHCOOH is the strongest acid and the lowest pKa.

2- ClCH2COOH is a strong acid, but no more than the first. Medium pKa value.

3- ClCH2CH2COOH is a strong acid, but no more than the two previous acids. High pKa value.

4- CH3CH2COOH is the weakest acid, so the highest pKa value.

Explanation:

The pKa values are the negative logarithm of dissociation constant. It represents the relative strengths of the acids. Stronger acids show smaller pKa values and weak acids present larger pKa value. The stronger the acid, the weaker it's the conjugate base. The larger the pKa of the conjugate base, the stronger the acid. The strength of an acid is inversely related to the strength of its conjugate.

Conjugate bases are the substance that has one less proton than the parent acid. The conjugate base of the acid presented in the problem are:

ClCH2COOH -> ClCH2COO- + H+

ClCH2CH2COOH -> ClCH2CH2COO- + H+

CH3CH2COOH -> CH3CH2COO- + H+

Cl2CHCOOH -> Cl2CHCOO - + H+

Cl2CHCOOH. The negative charge presented on its conjugate base is by resonance and inductive effect. This is the strongest acid.

ClCH2COOH. A negative charge is stabilized by resonance and electron-withdrawing but only one atom is present. So this acid is less strong than the first one.

ClCH2CH2COOH. The negative charge is stabilized by resonance and electron-withdrawing atom but the effect is less compared to the two acids showed previously.

CH3CH2COOH. The negative charge is stabilized by resonance and destabilized due to CH3 group. This is the weakest acid among the problem.

Stronger acids have smaller pKa values and weak acids have larger pKa values. Due to the information present in this problem, Cl2CHCOOH is the strongest acid and the lowest pKa. CH3CH2COOH is the weakest acid, so the highest pKa value.

Finally, we can conclude that according to their expected pKa values, the order of those acids should be:

1- Cl2CHCOOH is the strongest acid and the lowest pKa.

2- ClCH2COOH is a strong acid, but no more than the first. Medium pKa value.

3- ClCH2CH2COOH is a strong acid, but no more than the two previous acids. High pKa value.

4- CH3CH2COOH is the weakest acid, so the highest pKa value.

3 0

3 years ago

Calculate the rate constant at 200.°C for a reaction that has a rate constant of 8.30 × 10−4 s−1 at 90.°C and an activation ener

Sergeu [11.5K]

Answer:

23.0 s⁻¹ is rate constant

Explanation:

Using the Arrhenius equation:

k = A * e^(-Ea/RT)

Where k is rate constant

A is frequency factor (1.5x10¹¹s⁻¹)

Ea is activation energy = 55800J/mol

R is gas constant (8.314J/molK)

And T is absolute temperature (24°C + 273 = 297K)

Replacing:

k = 1.5x10¹¹s⁻¹ * e^(-55800J/mol/8.314J/molK*297K)

k = 1.5x10¹¹s⁻¹ * 1.53x10⁻¹⁰

k = 23.0 s⁻¹ is rate constant i hope this helpsss

Explanation:

4 0

3 years ago