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Blababa [14]
2 years ago
7

Black holes cannot be seen. However scientists think that black holes exist because of their effect on surrounding matter. Descr

ibe another force or phenomenon that cannot be seen directly. Give examples of the effects of this force on everyday objects.
BTW this is not the right subject but there is no astronomy category so I am using this subject.
Chemistry
2 answers:
san4es73 [151]2 years ago
5 0

Answer:

l

Explanation:

l

lara31 [8.8K]2 years ago
4 0

Answer:

If Black Holes Are "Black," How Do Scientists Know They Are There? A black hole can not be seen because strong gravity pulls all of the light into the middle of the black hole. But scientists can see how the strong gravity affects the stars and gas around the black hole.

Explanation:

some examples; 1. Pushing a wheel barrow.

2. Opening or closing a door.

3. Squeezing wet clothes.

4. Gravitational force.

5. Brakes applied to stop a moving vehicle.

6. A football kicked harder that decreases due to the frictional force.

7. Rubbing a glass rod with a silk.

8. Pressure applied on a pin of a notice board.

9. Running

10. Pushing

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14...........................
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What is the first stroke of a 4 stroke cycle?
lisabon 2012 [21]

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A

Explanation:

its a because that is the first thing you do

8 0
3 years ago
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if you are using a formula where you need the change in temperature, explain why it is not important whether your temperatures a
alexandr1967 [171]

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This is because, Kelvins and Celcius degrees both agree at fixed points i.e; the lower fixed point and upper

5 0
3 years ago
How many grams of Fe can be produced when 5.50 g of Fe2O3 reacts?
vichka [17]

Answer:

3,85 g of Fe

Explanation:

1- The first thing to do is calculate the molar mass of the Fe2O3 compound. With the help of a periodic table, the weights of the atoms are searched, and the sum is made:

Molar mass of Fe2O3 = (2 x mass of Fe) + (3 x mass of O) = 2 x 55.88 g + 3 x 15.99 g = 159.65 g / mol

Then, one mole of Fe2O3 has a mass of 159.65 grams.

2- Then, the relationship between the Fe2O3 that will react and the iron to be produced. With the previous calculation, we can say that with one mole of Fe2O3, two moles of Fe can be produced. Passing this relationship to the molar masses, it would be as follows:

1 mole of Fe2O3_____ 2 moles of Fe

159.65 g of Fe2O3_____ 111.76 g of Fe

3- Finally, the calculation of the mass that can be produced of Fe is made, starting from 5.50 g of Fe2O3

159.65 g of Fe2O3 _____ 111.76 g of Fe

5.50 g of Fe2O3 ______ X = 3.85 g of Fe

<em>Calculation: 5.50 g x 111.76 g / 159.65 g = 3.85 g </em>

The answer is that 3.85 g of Fe can be produced when 5.50 g of Fe2O3 react

7 0
3 years ago
An analytical chemist is titrating 118.3 mL of a 0.3500 M solution of butanoic acid (HC3H7CO2) with a 0.400 M solution of KOH. T
TEA [102]

Answer:

pH = 12.33

Explanation:

Lets call HA = butanoic acid and A⁻ butanoic acid and its conjugate base butanoate respectively.

The titration reaction is

HA + KOH ---------------------------- A⁻ + H₂O + K⁺

number of moles of HA :   118.3 ml/1000ml/L x 0.3500 mol/L = 0.041 mol HA

number of  moles of OH  : 115.4 mL/1000ml/L x 0.400 mol/L  = 0.046 mol A⁻

therefore the weak acid will be completely consumed and what we have is  the unreacted strong base KOH which will drive the pH of the solution since the contribution of the conjugate base is negligible.

n unreacted KOH = 0.046 - 0.041 = 0.005 mol KOH

pOH = - log (KOH)

M KOH = 0.005 mol / (0.118.3 +0.1154)L = 0.0021 M

pOH = - log (0.0021) = 1.66

pH = 14 - 1.96 = 12.33

Note: It is a mistake to ask for the pH of the <u>acid solutio</u>n since as the above calculation shows we have a basic solution the moment all the acid has been consumed.

4 0
3 years ago
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