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krek1111 [17]
3 years ago
7

Help me please ive been here for hours

Chemistry
1 answer:
ANEK [815]3 years ago
3 0

Answer:

A- Before the mechanic left, the molecules were moving away from each other. When she returned, they were moving around each other.

Explanation:

Brainliest?

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a candle is placed between a concave mirror and its focal point which two of the following best describe the image​
Stels [109]

Answer:

Beyond the centre of curvature

Explanation:

4 0
3 years ago
5. How can you tell the difference between CuS and Cu2S
puteri [66]

Answer:

Density, melting point. and magnetic properties  

Explanation:

I can think of three ways.

1. Density

The density of Cu₂S is 5.6 g/cm³; that of CuS is 4.76 g/cm³.

It should be possible to distinguish these even with high school equipment.

2. Melting point

Cu₂S melts at 1130 °C (yellowish-red); CuS decomposes at 500 °C (faint red).

A Bunsen burner can easily reach these temperatures.

3. Magnetic properties

You can use a Gouy balance to measure the magnetic susceptibilities.

In Cu₂S the Cu⁺ ion has a d¹⁰ electron configuration, so all the electrons are paired and the solid is diamagnetic.

In CuS the Cu²⁺ ion has a d⁹ electron configuration, so all there is an unpaired electron and the solid is paramagnetic.

A sample of Cu₂S will be repelled by the magnetic field and show a decrease in weight.

A sample of CuS will be attracted by the magnetic field and show an increase in weight.

In the picture below, you can see the sample partially suspended between the poles of an electromagnet.

 

6 0
4 years ago
How do you create a neutrally buoyant object using 3 or more objects?
olga_2 [115]
It has to weigh the same weight as the amount of water it displaces. eg - if it weighs a kg, it would have to displaces exactly 1 litre of water
3 0
3 years ago
How does wind cause weathering?
pantera1 [17]

Hello!! WOW, what a coincidence! I just took this lesson and quiz yesterday, so the answer is still fresh in my mind!

The answer to your question is

D) Blowing sand can wear away a rock's surface and break it into smaller pieces

When wind blows, sure it can pick up dry soil and sand and relocate it, but that doesn't cause the weathering in rocks.

Wind doesn't create new landforms either, that comes from plate tectonic movements and other things.

I just eliminated B and C with the two sentences above, I really don't know how to eliminate A, just common sense i guess.

Please give me brainliest if I was correct and helpful!

Otherwise, please comment and let me know how I can fix my answer!

Thank you, it was fun, have a nice week!

4 0
3 years ago
Read 2 more answers
Calculate the change in energy when 75.0 grams of water drops from<br> 31.0C to 21.6.
zysi [14]

Answer: Step 1: Calculate qsur (the surrounding is

usually the water)

qsur = ? J

m = 75.0 g water

c = 4.184 J/g

oC

ΔT = (Tfinal- Tinitial)= (21.6 – 31.0) = -9.4 oC

qsur = m · c · (ΔT)

qsur = (75.0g) (4.184 J/g

oC) (-9.4 oC)

qsur = - 2949.72 J

First, using the information we know that we

must solve for qsur, which is the water. We know

the mass for water, 75.0g, the specific heat of

the water, 4.184 j/g

o

c, and the change in

temperature, 21.6-31.0 = -9.4 oC. Plugging it

into the equation, we solve for qsur.

Step 2: Calculate qsys qsys = - (qsur)

qsys = - (- 2949.72 J)

qsys = + 2949.72

In this case, the qsur is negative, which means

that the water lost energy. Where did it go? It

went to the system. Thus, the energy of the

system is negative, opposite, the energy of the

surrounding.

Step 3: Calculate moles of the substance

that is the system

Given: 12.8 g KCl

Mol system = (g system given)

(molar mass of system)

Mol system = (12.8 g KCl)

(39.10g + 35.45g)

Mol system = 12.8 g KCl

74.55 g

Mol system = 0.172

Here, we solve for the mol in the system by

using the molar mass of the material in the

system.

Step 4: Calculate ΔH ΔH = q sys .

Mol system

ΔH= + 2949.72 J

0.172 mol

ΔH= +17179.81 J/mol or +1.72 x 104

J/mol

i hope this helps

5 0
3 years ago
Read 2 more answers
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