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3 years ago

Q.2. How does the valency of elements vary in going down a group of the periodic table?

Chemistry

1 answer:

Elan Coil [88]3 years ago

8 0

Answer:

The valency does not change going down a group since the bonding behavior is not affected by the core electrons.

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Which describes the role of energy in photosynthesis and cellular respiration?

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A) Energy is needed to start photosynthesis and is a product of cellular respiration.

Explanation:

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3 years ago

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Magnesium nitrate contains chemical bonds that are

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Answer:

Magnesium Nitrate is an ionic compound formed by:

Magnesium;Mg+2 (the cation) and Nitrate NO−3 (the poly-atomic anion).

In order for these two ions to bond, the charges must be equal and opposite. Therefore, it will take:

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2 years ago

A solution was prepared by dissolving 195.0 g of KCl in 215 g of water. Calculate the mole fraction of KCl. (The formula weight

defon

Answer:

Approximately $0.180$ .

Explanation:

The mole fraction of a compound in a solution is:

$\displaystyle \frac{\text{Number of moles of compound in question}}{\text{Number of moles of all particles in the solution}}$ .

In this question, the mole fraction of $\rm KCl$ in this solution would be:

$\displaystyle X_\mathrm{KCl} = \frac{n(\mathrm{KCl})}{n(\text{All particles in this soluton})}$ .

This solution consist of only $\rm KCl$ and water (i.e., $\rm H_2O$ .) Hence:

$\begin{aligned} X_\mathrm{KCl} &= \frac{n(\mathrm{KCl})}{n(\text{All particles in this soluton})}\\ &= \frac{n(\mathrm{KCl})}{n(\mathrm{KCl}) + n(\mathrm{H_2O})}\end{aligned}$ .

From the question:

Mass of $\rm KCl$ : $m(\mathrm{KCl}) = 195.0\; \rm g$ .
Molar mass of $\rm KCl$ : $M(\mathrm{KCl}) = 74.6\; \rm g \cdot mol^{-1}$ .

Mass of $\rm H_2O$ : $m(\mathrm{H_2O}) = 215\; \rm g$ .
Molar mass of $\rm H_2O$ : $M(\mathrm{H_2O}) = 18.0\; \rm g\cdot mol^{-1}$ .

Apply the formula $\displaystyle n = \frac{m}{M}$ to find the number of moles of $\rm KCl$ and $\rm H_2O$ in this solution.

$\begin{aligned}n(\mathrm{KCl}) &= \frac{m(\mathrm{KCl})}{M(\mathrm{KCl})} \\ &= \frac{195.0\; \rm g}{74.6\; \rm g \cdot mol^{-1}} \approx 2.61\; \em \rm mol\end{aligned}$ .

$\begin{aligned}n(\mathrm{H_2O}) &= \frac{m(\mathrm{H_2O})}{M(\mathrm{H_2O})} \\ &= \frac{215\; \rm g}{18.0\; \rm g \cdot mol^{-1}} \approx 11.9\; \em \rm mol\end{aligned}$ .

The molar fraction of $\rm KCl$ in this solution would be:

$\begin{aligned} X_\mathrm{KCl} &= \frac{n(\mathrm{KCl})}{n(\text{All particles in this soluton})}\\ &= \frac{n(\mathrm{KCl})}{n(\mathrm{KCl}) + n(\mathrm{H_2O})} \\ &\approx \frac{2.61 \; \rm mol}{2.61\; \rm mol + 11.9\; \rm mol} \approx 0.180\end{aligned}$ .

(Rounded to three significant figures.)

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3 years ago

FOR 100 PTS

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Answer:

B.) A hot liquid or air that expands, becomes less dense, and rises or becomes more dense and sinks.

Explanation:

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4 years ago

Draw the structural formula of the major product of the reaction of (S)-2,2,3-trimethyloxirane with MeOH, H . Use the wedge/hash

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Answer:

(S)-3-methoxy-3-methylbutan-2-ol

Explanation:

In this case, we have an epoxide opening in acid medium. The first step then is the protonation of the oxygen. Then the epoxide is broken to generate the most stable carbocation. The nucleophile ( $CH_3OH$ ) will attack the carbocation generating a new bond. Finally, the oxygen is deprotonated to obtain an ether functional group and we will obtain the molecule (S)-3-methoxy-3-methylbutan-2-ol.

See figure 1

I hope it helps!

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4 years ago

Q.2. How does the valency of elements vary in going down a group of the periodic table?​

Q.2. How does the valency of elements vary in going down a group of the periodic table?