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postnew [5]
3 years ago
11

For each example of a phase change, identify whether heat is absorbed from the surroundings or

Chemistry
1 answer:
vladimir1956 [14]3 years ago
4 0

In case of popsicle and alcohol, heat is absorbed from the surrounding.

In case of lava heat is emitted into the surrounding.

<h3><u>Explanation:</u></h3>

Melting of popsicle is just a change of state from solid to liquid. This is the phenomenon which occurs when the popsicle gets the heat from the surrounding and it absorbs the heat, thereby turning into liquid. So it absorbs heat from the surrounding.

The alcohol when spread on the skin evaporates into vapour. This is the phenomenon of evaporation which occurs when alcohol absorbs heat from the surrounding and thereby turning into vapour.

Similarly, when lava solidifies into solid, the change of state occurs. As lava emits heat into the surrounding, the temperature of the lava goes down, thereby changing it into solid. So it emits heat into surrounding.

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3) A certain reaction has the following general form: A + B à AB At a particular temperature the concentration versus time were
seropon [69]

Answer:

a. First order.

b. k=3.7x10^{-3}s ^{-1}

c. t_{1/2}=187.3s

d. [A]=0.111M

Explanation:

Hello.

a. In this case since the slope is in s⁻¹ we can infer that the lineal form of the rate law is:

ln[A]=-kt+ln[A]_0

Which is also:

y=mx+b

It means that the reaction is first-order as slope equals the negative of the rate constant which also has units of first-oder reaction.

b. Since the slope is −3.7 x 10−3 s−1 the rate constant is:

k=-m\\\\k=-(-3.7x10^{-3}s ^{-1})\\\\k=3.7x10^{-3}s ^{-1}

c. For first-order reactions, the half-life is:

t_{1/2}=\frac{ln(2)}{k}\\ \\t_{1/2}=\frac{ln(2)}{3.7x10^{-3}s^{-1}}\\\\t_{1/2}=187.3s

d. In this case, since the integrated first-order rate law is:

[A]=[A]_0exp(-kt)

The concentration once 220 seconds have passed is:

[A]=0.250Mexp(-3.7x10^{-3}s^{-1}*220s)\\\\

[A]=0.111M

Regards.

7 0
3 years ago
What is the percent by mass of magnesium sulfate in MgSO4 · 7H2O?
Degger [83]

Answer: 48.83%

Explanation: Mass percent is the ratio of mass of the particular substance  to the total mass of given compound.

{\text {mass percentage}}=\frac{\text{mass of }MgSO_4}{\text {total mass}}\times 100\%

Mass of MgSO_4= 120g

Mass of MgSO_4.7H_2O= 246g

{\text {mass percentage}}=\frac{120g}{246g}\times 100\%=48.83\%

8 0
3 years ago
How kids today make slime and why each ingredient is used. What does each ingredient do and what happens if you change how much
Igoryamba

Answer:

Find the steps and explanation below.

Explanation:

A. Kids make slime following these basic steps;

1. In a bowl, is 1/4 cup of water is added to 1 oz. of glue. Add coloring if you wish to.

2. 1/4 cup of Borax solution, also known as Sodium Tetraborate is added to the mixture and gradually stirred.

3. The mixture is kneaded with the hands to ensure a smooth consistency.

4. Water remnants are discarded and the slime is stored in a plastic bag and kept in the fridge.

B.

What each ingredient does

Polyvinyl acetate present in the glue acts as a liquid polymer.

Borax binds the liquid polymers together.

Water eases the mixing process

C.

If lesser ingredients are used, the slime will not have its characteristic slimy nature. If excess of the ingredients are used, the slime becomes very sticky.

4 0
3 years ago
A block of aluminum occupies a volume of 15.0 ML and weighs 40.5 gallons what is the density
svlad2 [7]

Hello!

I'm going to have to infer that you meant "grams" and not "gallons" :-)

Anyways, to find the density, you need to the divide mass over volume (d = m/V).

Since we are given the volume being 15.0 mL, and the weight being 40.5 grams, we can find the density of the aluminum block.

40.5 grams / 15.0 mL = 2.7 g/mL

Therefore, the density of the aluminum block is 2.7 grams per milliliter.

4 0
3 years ago
Read 2 more answers
What happens when the concentration of water inside a cell is lower than the concentration of water outside the cell?
adell [148]

Answer:

Water outside the cell will flow inwards by osmosis to attain equilibrium

Explanation:

In the hypotonic environment, the concentration of water is greater outside the cell and the concentration of solute is higher inside. A solution outside of a cell has a lower concentration of solutes relative to the cytosol.

If concentrations of dissolved solutes are greater inside the cell, the concentration of water inside the cell is correspondingly lower. As a result, water outside the cell will flow inwards by osmosis to attain equilibrium.

Osmosis is a process by which molecules of a solvent tend to pass from a less concentrated solution into a more concentrated one through a semipermeable membrane.

4 0
3 years ago
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