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SSSSS [86.1K]
3 years ago
6

The universe contains billions of galaxies, each containing billions of stars. True or false

Chemistry
2 answers:
Tatiana [17]3 years ago
8 0
True but no one know Exactly how many stars there are
Komok [63]3 years ago
6 0
This is true but there could be more stars and galaxies.
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A change in state is a physical change.<br><br>True or false​
Morgarella [4.7K]

Answer: Depending on the state of change it can be a physical change. Example: Evaporation is the physical change of a liquid turned into a gas.

That said, I'm pretty sure the answer is (True)

Note: Hope this is correct and it helps. Good luck :)

5 0
3 years ago
An experiment to measure the enthalpy change for the reaction of aqueous
Komok [63]

Given that, an experiment to measure the enthalpy change for the reaction of aqueous copper(II) sulfate, CuSO4(aq) and zinc, Zn(s) was carried out in a coffee cup calorimeter; the heat of the reaction in the whole system is calculated to be 2218.34 kJ

Heat of reaction (i.e enthalpy of reaction) is the quantity of heat that is required to be added or removed when a chemical reaction is taken place in order to maintain all of the compounds present at the same temperature.

The formula used to calculate the heat of the reaction can be expressed as follows:

Q = mcΔT

where:

  • Q = quantity of heat transfer
  • m = mass
  • c = specific heat of water = 4.18 kJ/g °C (constant)
  • ΔT = change in temparature

From the information given:

  • The initial temperature (T₁) = 25° C
  • The final temperature (T₂) = 91.5° C

∴

The change in temperature i.e. ΔT = T₂ - T₁

ΔT = 91.5° C - 25° C

ΔT = 66.5° C

The number of moles of CuSO₄ = 1.00 mol/dm³ × 50.0 cm³

\mathbf{= (1 \times \dfrac{50}{1000})\ moles}

= 0.05 moles

  • Since the molar mass of CuSO₄ = 159.609 g/mol

Then;

Using the relation:

\mathbf{number \ of \ moles = \dfrac{mass}{molar \ mass}}}

By crossing multiplying;

mass of CuSO₄ = number of moles of CuSO₄ ×  molar mass of CuSO₄

mass of CuSO₄ = 0.05 moles  × 159.609 g/moles

mass of CuSO₄ = 7.9805 grams

∴

Using the formula from above:

Q = mcΔT

Q = 7.9805 g × 4.18 kJ/g °C × 66.5° C

Q = 2218.34 kJ

Therefore, we can conclude that the heat of the reaction is 2218.34 kJ

Learn more about the chemical reaction here:

brainly.com/question/20250226?referrer=searchResults

8 0
3 years ago
Please Help me
dangina [55]
Democritus was the first to propose the idea of the atom. He said the atom was just this tiny, solid sphere. However, he used no scientific evidence to support his claim, so a guy named John Dalton did some experimenting and basically backed up Democritus' claim with evidence. Then, a guy named J.J. Thompson came along and said the atom was not solid and that is consisted of tiny negatively charged particles(electrons) and he came up with the Plum Pudding model which is just a tiny sphere with a punch of random scattered dots in it. After that, Ernest Rutherford did experiments and found that the tiny sphere is made up of mostly empty space with a tiny, dense, positively charged sphere inside of it, and the negatively charged particles just randomly float around it. Neils Bohr then said that the electrons take specific, circular, evenly spaced paths. Then, finally, we come to the Quantum Mechanical Model which is the one accepted today. This model basically vetos Bohr's idea and has a nucleus inside of an electron cloud, which is where the electrons are found.
6 0
3 years ago
Two atoms with the same number of protons but a different number of neutrons are
Luda [366]
They are called isotopes.

Example of isotopes are Hydrogen and deuterium.
Hydrogen is 1 proton and 0 neutrons.
Deuterium is 1 proton and 1 neutron
6 0
4 years ago
In some regions of the world, forests are cut down and then burned to create room for farmland. How might this local environment
UkoKoshka [18]

The answer is D.

<u>Explanation</u>

Without trees, no carbon dioxide will be released into the air. It would not raise oxygen levels, and it wouldn’t effect rising sea levels.

6 0
3 years ago
Read 2 more answers
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