CHEMISTRY HIGH SCHOOL

Which of the following examples depict(s) a physical property?

Answers

Answer 1

Answer:

Answer:

$\boxed {\tt D. \ All \ of \ the \ above }$

Explanation:

A physical property is a property that can be observed without changing the composition.

Some examples of physical properties are:

Color
Density
Length
Mass
Smell
Temperature
Boiling Point
Hardness

Now, let's examine our answer choices.

Choice A: Sugar is white in color

The property is color, which is a physical property.

Choice B: Iron is more dense than aluminum

The property is density, which is a physical property.

Choice C: Diamond is harder than graphite.

The property is hardness, which is a physical property.

Since all three choices depict physical properties, the best choice is D. All of the above.

Answer 2

Answer:

Answer:

Explanation:

All explain physical no chemical examples were given

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Answers

The answer would be A

When double-stranded DNA is heated at neutral pH, which change does not occur? A) The absorption of ultraviolet (260 nm) light increases.
B) The covalent N-glycosidic bond between the base and the pentose breaks.
C) The helical structure unwinds.
D) The hydrogen bonds between A and T break.
E) The viscosity of the solution decreases.

Answers

Answer:

B) The covalent N-glycosidic bond between the base and the pentose breaks

Explanation:

When forces that bind 2 DNA strands are broken, these strands finally split. This process is called denaturalization

The main forces that remain both DNA strands together are the hydrogen bonds (physical forces), between pair of bases (Adenine with Thymine, and Guanine with Cytosine)

Denaturalization may occur by different factor: Ph alteration, salt addition, temperature (heating), etc

When heating a DNA solution, denaturalization process may be followed using UV absorption (normally, at wavelength of 260 nm): when DNA (double strand) has its regular structure, UV light absorption is low, as the nitrogen bases are stacked like a pile of coins, for which structure absorbs less light

When DNA structure is denaturalized, these nitrogen bases are exposed, and UV absorption increases

Also, DNA denaturalization may be followed by viscosity: for a double strand DNA solution, viscosity is high due to double chain stiffness but when strands are denaturalized, simple strands solution are less viscous (so viscosity decreases over time, when heating the solution)

Lastly, when solution is heated, only physical forces are broken (hydrogen bonds) and not chemical bonds (such as covalent bonds), for which extreme conditions are needed

Express 750 dg in g.

Answers

Dg stands for 10 (from Greek Deka, ten) , so 1 decagram is 10 grams.

750 decagrams is then equivalent to 750*10 grams, which is also 7500 grams (it's also 7.5 kg).

H2(g) + CO2(g) + 10 kcal H2O(g) + CO(g)In another experiment involving the above reaction at 1,000°C, the equilibrium concentrations were found to be:

H2(g) = 2.0 moles per liter
H2O(g) = 4.0 moles per liter
CO2(g) = 5.0 moles per liter
CO(g) = 4.0 moles per liter

What is the equilibrium constant, Keq, for this reaction?

Answers

Answer: The equilibrium constant for the given reaction is 0.8

Explanation:

Equilibrium constant is defined as the ratio of concentration of the products raised to the power its stoichiometric coefficients to the concentration of reactants raised to power its stoichiometric coefficient. It is represented as $K_c$

For the general equation:

$aA+bB\rightleftharpoons cC+dD$

The equilibrium constant is represented as:

$K_c=([C]^c[D]^d)/([A]^a[B]^b)$

For the given chemical equation:

$H_2(g)+CO_2(g)+10 kcal\rightleftharpoons H_2O(g)+CO(g)$

$K_c$ for this equation is given by:

$K_c=([H_2O][CO])/([H_2][CO_2])$

Concentration at equilibrium of

$H_2=2mol/L\nH_2O=4mol/L\nCO_2=5mol/L\nCO=4mol/L$

Putting values in above equation, we get:

$K_c=(4* 4)/(2* 5)\nK_c=0.8$

Hence, the equilibrium constant for the given chemical reaction is 0.8

This might be a little hard for me but I got it. So you have 2.0, 4.0, 5.0 and 4.0. Subtract from 3.0 - 2.0 = 1.0 and 4.5 - 2.0 = 2.5.

So now we have other answers.

H20, H2, CO2 and CO

Keq reaction for each formula is 1.6

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The atomic theory has been revised many times over the last several hundred years. John Dalton described the atom as a solid sphere while later scientists such as J.J. Thomson and Ernest Rutherford developed different models of the atom. Why has the atomic theory changed so much over the last several centuries?
A new scientific method helps scientists form more efficient theories and models.
As new discoveries are made, existing theories are revised or replaced.
The atom has changed over time, and new theories must reflect those changes.
Scientists with different opinions

Answers

The answer is: As new discoveries are made, existing theories are revised or replaced.

Dalton stated that atom is matter that can not be divided.

His "plum pudding" model (1904) suggested: the electrons are embedded in the positive charge.

J. J. Thomson discovered the electron in 1897.

According to Rutherford model of the atom:

1) Atoms have their charge concentrated in a very small nucleus.

2) Major space in an atom is empty.

3) Atoms nucleus is surrounded by negatively charged particles called electrons.

4) An atom is electrically neutral.

As new discoveries are made, existing theories are revised or replaced.

Which solution has the lowest freezing point

Answers

bc KI has a lower freezing point than water. this means that the higher ratio of KI to water you have, the lower the freezing point will be. since 3 has the highest ratio of KI to water, it will have the lowest freezing point

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