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Juliette [100K]
3 years ago
14

A school has 8 period in a day such the each periods is of 35 minutes.lf the number of period is reduced to 7, then how long wou

ld each period be?​
Chemistry
1 answer:
scZoUnD [109]3 years ago
5 0

Answer:

45 minutes about

Explanation:

i think because i have 7 periods with 45 minutes each

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The reaction between hydrogen gas and chlorine gas produces hydrogen chloride according to the following equation: H2(g) + Cl2(g
Andreyy89

Answer:

The enthalpy of reaction is -185 kJ

Explanation:

To get the reaction:

 H₂(g) + Cl₂(g) → 2 HCl(g)

you must follow the following steps:

<em>1)  Reactive molecules must break their bonds to obtain their atoms.</em>

H₂(g) → 2 H(g)

Cl₂(g) → 2 Cl(g)

Bond energy (or enthalpy) is the energy required to break one mole of bonds of a gaseous substance. In the case of diatomic molecules with a single bond, it corresponds to the energy necessary to dissociate 1 mole of said substance in the atoms that form it.

Whenever you want to break links you must supply energy, so the link enthalpy will have positive values; while when a mole of bonds is formed energy is released and the bond enthalpy of this process will be negative.

In this case you will then have:

H₂(g) → 2 H(g)           ΔH=436 kJ/mol

Cl₂(g) → 2 Cl(g)         ΔH=243 kJ/mol

So the total energy needed to break all the bonds is:

ΔH=1 mol*436 kJ/mol +1 mol* 243 kJ/mol= 679 kJ

2) The atoms that were obtained in the break of the bonds must be combined to obtain the product.

2 H (g) + 2 Cl (g) → 2 HCl (g)

Being the single bond energy for one mole of 431 kJ H-Cl bonds and considering that two moles of H-Cl bonds are formed, the ΔH is:

ΔH = -2 moles* (432 kJ/mol) = -864 kJ

As mentioned, when a mole of bonds is formed energy is released, the bond enthalpy of this process will be negative.  So the formation of HCl is negative.

Hess's law states that the energy change in an overall chemical reaction is equal to the sum of the energy changes in the individual reactions comprising it. So:

ΔHtotal= -864 kJ + 679 kJ

ΔHtotal= -185 kJ

<u><em>The enthalpy of reaction is -185 kJ</em></u>

3 0
3 years ago
Lead crystallizes in a face-centered cubic structure with a density of 11.34 g/cm3. Polonium crystallizes in a simple cubic stru
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Answer:

Explanation:

In a face-centered cubic structure, each unit cell has 4 atoms. Each of the 8 corner atoms contribute 1/8 part to the unit cell and each of the 6 atoms at face-centres contribute 1/2 part to the unit cell. So, each unit cell has net 4 atoms.

In a simple cubic structure, there are 8 atoms, one at each corner. So, each one of them contribute 1/8 part to the unit cell. So, the unit cell has only 1 atom effectively.

Hence, each cell units of lead has 4 times as atoms as in the unit cells of polonium.

Due to this, density of lead is higher despite the fact that it's atomic mass is smaller and the size is bigger than that of a polonium atom.

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3 years ago
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(I posted the picture for a ray diagram and the first law of reflection.) The rays show the first law of reflection since everything gets reflected. Look at the picture for more:

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Wave energy is dissipated in quiet water areas like bays, resulting in sand deposition. Strong wave energy concentrates its power on the wave-cut cliff, eroding areas that stick out into the water. The wave erodes the cliff's bottom, eventually causing it to fall.

Explanation:

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