What happens in a chemical reaction?

The walls in your home have 25mm of expanded polystyrene (R-value 3.96) and 25mm of rigid urethane foam (R-value 7.50). What is

Finger [1]

Answer:

3.6 per inch

EPS insulation features an average r-value of 3.6 per inch.

In addition to providing energy efficiency, EPS without film facers has a perm rating of up to 5.0.

Explanation:

hope this helps

7 0

3 years ago

What is the mass of a sample of water that takes 2000 kJ of energy to boil into steam at 373 K. The latent heat of vaporization

Arte-miy333 [17]

Answer:

0.89kg

Explanation:

Q=mL L=specific latent heat

Q=energy required in J

m=mass in Kg

Q=mL

m=Q/L

m=2000000J/2.25 x 10^6 J kg-1

m=0.89kg

3 0

3 years ago

Consider the following reaction mechanism:

snow_lady [41]

Answer:

Step 2 (the slow step).

Explanation:

The rate-determining step is always the slow step of a mechanism.

That is so, because it is the slow step which limits the reaction.

Imaging that for assembling a toy you have process of three steps:

1. order ten pieces, which you can do in 1 minute: meaning that you can order order the pieces for 60/1 = 60 toys in 1 hour.

2. glue the pieces and hold the toy until the glue hardens, which takes 1 hour: meaning finishingh 1 toy in 1 hour.

3. pack the toy, which takes 2 minutes: meaning that you can pack 60/2 = 30 toys in one hour.

The time to glue and hold one toy until the glue hardens determines that you can assemble 1 toy in 1 hour and not 60 toys or 30 toys.

Thus, the step that determines the rate at which the reaction happens is the slowest step: step 2.

3 0

3 years ago

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A 50/50 blend of engine coolant and water (by volume) is usually used in an automobile's engine cooling system. If a car's cooli

Diano4ka-milaya [45]

Answer:

$\large \boxed{109.17 \, ^{\circ}\text{C}}$

Explanation:

Data:

50/50 ethylene glycol (EG):water

V = 4.70 gal

ρ(EG) = 1.11 g/mL

ρ(water) = 0.988 g/mL

Calculations:

The formula for the boiling point elevation ΔTb is

$\Delta T_{b} = iK_{b}b$

i is the van’t Hoff factor — the number of moles of particles you get from 1 mol of solute. For EG, i = 1.

1. Moles of EG

$\rm n = 0.50 \times \text{4.70 gal} \times \dfrac{\text{3.785 L}}{\text{1 gal}} \times \dfrac{\text{1000 mL}}{\text{1 L}} \times \dfrac{\text{1.11 g}}{\text{1 mL}} \times \dfrac{\text{1 mol}}{\text{62.07 g}} = \text{159 mol}$

2. Kilograms of water

$m = 0.50 \times \text{4.70 gal} \times \dfrac{\text{3.785 L}}{\text{1 gal}} \times \dfrac{\text{998 g}}{\text{1 L}} \times \dfrac{\text{1 kg}}{\text{1000 g}} = \text{8.88 kg}$

3. Molal concentration of EG

$b = \dfrac{\text{159 mol}}{\text{8.88 kg}} = \text{17.9 mol/kg}$

4. Increase in boiling point

$\rm \Delta T_{b} = iK_{b}b = 1 \times 0.512 \, \, ^{\circ}\text{C} \cdot kg \cdot mol^{-1} \, \times 17.9 \cdot mol \cdot kg^{-1} = 9.17 \, ^{\circ}\text{C}$

5. Boiling point

$\rm T_{b} = T_{b}^{\circ} + \Delta T_{b} = 100.00 \, ^{\circ}\text{C} + 9.17 \, ^{\circ}\text{C} = \mathbf{109.17 \, ^{\circ}C}\\\rm \text{The boiling point of the solution is $\large \boxed{\mathbf{109.17 \, ^{\circ}C}}$}$

7 0

3 years ago

Which mineral leaves a green-black powder when rubbed against an unglazed porcelain plate

solong [7]

Answer:

Pyrite leaves behind a green-black streak when it is rubbed against an unglazed porcelain plate as a part of the streak test process.

Explanation:

Different minerals produce different coloured streaks when rubbed against a white ceramic or porcelain streak plate. This streak test is done to identify the mineral and distinguish the same from other minerals that look similar in colour and texture.

It must be ensured that the test is done on clean and fresh specimens of the mineral and that there must be no contaminants. Pyrite specimens are usually brass-yellow colour but it leaves a green-black streak when the streak test is done.

4 0

3 years ago