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3 years ago

Which of the following statements holds true for a chemical change?

Chemistry

2 answers:

Anettt [7]3 years ago

8 0

C. in a chemical change the molecular structure changes.

ad-work [718]3 years ago

6 0

Answer : The correct option is C.

Explanation :

Chemical change : It is defined as a change in which a new compounds are formed by the chemical reaction. Changes occurs in their chemical composition and properties.

The molecular structure of a substance changes in a chemical reaction is a chemical change.

Change in molecular structure means that there is a breaking and formation of bonds in a molecule.

The example of chemical change in terms of change in molecular structure is the reaction of hydrogen with oxygen.

The reaction of hydrogen with oxygen is,

$H_2(g)+O_2(g)\rightarrow 2H_2O(l)$

In this reaction, the H-H bond is break and O-H bond is form.

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A sample of cacl2⋅2h2o/k2c2o4⋅h2o solid salt mixture is dissolved in ~150 ml de-ionized h2o. the oven dried precipitate has a ma

Paraphin [41]

We are given that the balanced chemical reaction is:

cacl2⋅2h2o(aq) + k2c2o4⋅h2o(aq) ---> cac2o4⋅h2o(s) + 2kcl(aq) + 2h2o(l)

We known that the product was oven dried, therefore the mass of 0.333 g pertains only to that of the substance cac2o4⋅h2o(s). So what we will do first is to convert this into moles by dividing the mass with the molar mass. The molar mass of cac2o4⋅h2o(s) is molar mass of cac2o4 plus the molar mass of h2o.

molar mass cac2o4⋅h2o(s) = 128.10 + 18 = 146.10 g /mole

moles cac2o4⋅h2o(s) = 0.333 / 146.10 = 2.28 x 10^-3 moles

Looking at the balanced chemical reaction, the ratio of cac2o4⋅h2o(s) and k2c2o4⋅h2o(aq) is 1:1, therefore:

moles k2c2o4⋅h2o(aq) = 2.28 x 10^-3 moles

Converting this to mass:

mass k2c2o4⋅h2o(aq) = 2.28 x 10^-3 moles (184.24 g /mol) = 0.419931006 g

Therefore:

The mass of k2c2o4⋅<span>h2o(aq) in the salt mixture is about 0.420 g</span>

3 0

3 years ago

Read 2 more answers

The mass of a single uranium atom is 4.70x10^-22 grams. How many uranium atoms would there be in 111 milligrams of uranium?

emmainna [20.7K]

2.4 x 10²² atoms

<h3>Further explanation</h3>

Atomic mass is the average atomic mass of all its isotopes

In determining the mass of an atom, as a standard is the mass of 1 carbon-12 atom whose mass is 12 amu

So the atomic mass obtained is the mass of the atom relative to the 12th carbon atom

mass single Uranium atom=4.7 x 10⁻²² g

then for 111 mg=0.111 g

$\tt \dfrac{0.111}{4.7\times 10^{-22}}=2.4\times 10^{22}$

5 0

3 years ago

Use the idea of diffuseition to explain how the smell of perfume travel

pogonyaev

When perfume is sprayed in a room the particles of perfume diffuse with the particles in the air.

6 0

3 years ago

How many Joules does it take to raise 1 g of water 2°C

Romashka-Z-Leto [24]

Answer:

Quantitative experiments show that 4.18 Joules of heat energy are required to raise the temperature of 1g of water by 1°C. Thus, a liter (1000g) of water that increased from 24 to 25°C has absorbed 4.18 J/g°C x 1000g x 1°C or 4180 Joules of energy.

4 0

2 years ago

Calculate the enthalpy of formation of butane, C4H10, using the balanced chemical

melisa1 [442]

Answer:

-125.4

Explanation:

Target equation is 4C(s) + 5H2(g) = C4H10

These are the data equations for enthalpy of combustion

C(s) + O2(g) =O2(g) -393.5 kJ/mol * 4
H2(g) + ½O2(g) =H20(l) = 285.8 kJ/mol * 5
2CO2(g) + 3H2O(l) = 13/2O2 (g) + C4H10 - 2877.1 reverse

To get target equation multiply data equation 1 by 4; multiply equation 2 by 5; and reverse equation 3, so...

Calculate 4(-393.5) + 5(-285.8) + 2877.6 and you should get the answer.

7 0

3 years ago