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3 years ago

Which one of the following statements is not correct?

Chemistry

1 answer:

sweet [91]3 years ago

7 0

Answer:

option a, During allotropic transformation, the number of atoms in the material changes.

Explanation:

Allotrops are different crystalline forms of the same element. So, two allotrops of an element have same number of atoms.

for example diamond, graphite, graphene, fullerene are allotropic forms of carbon.

Allpotops differ in physical and chemical properties. So, volume changes during alloptropic transformation. So, statement b is correct.

Allotropic transformation is the transformation of one allotropic form to other therefore, number of atom does not change during allotropic transformation.

Chemical species having same atomic number or same no. of protons are called isotopes. so statement c is correct.

When an electron is added to the neutral element, electronic repulsion increases which lead to the increase in atomic size, So, statement d is also correct.

So among given, option a is incorrect

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analytical chemists can detect very small amounts of amoin acids , down to 3x10^-21 mol. how many molecules of an amino acid (mr

sesenic [268]

The number of particles in one mole is given be Avagadro's number <span>6.022×10^23

Multiply by number of moles.

3 ×10^-21 mol * 6.022 ×10^23 molecules/mol = </span><span>1,807 molecules
(rounded to nearest whole number)
</span>

6 0

3 years ago

Now they feel it is best to have you identify an unknown gas based on its properties. Suppose 0.508 g of a gas occupies a volume

pishuonlain [190]

Answer: Option (b) is the correct answer.

Explanation:

The given data is as follows.

mass = 0.508 g, Volume = 0.175 L

Temperature = (25 + 273) K = 298 K, P = 1 atm

As per the ideal gas law, PV = nRT.

where, n = no. of moles = $\frac{mass}{\text{molar mass}}$

Hence, putting all the given values into the ideal gas equation as follows.

PV = $\frac{mass}{\text{molar mass}} \times RT$

1 atm \times 0.175 L = $\frac{0.508 g}{\text{molar mass}} \times 0.0821 L atm/ K mol \times 298 K$

= 71.02 g

As the molar mass of a chlorine atom is 35.4 g/mol and it exists as a gas. So, molar mass of $Cl_{2}$ is 70.8 g/mol or 71 g/mol (approx).

Thus, we can conclude that the gas is most likely chlorine.

4 0

3 years ago

Pls help

Irina-Kira [14]

Answer:

CrO₂ --------------------> Cr⁴⁺ and O²⁻

VCO₃ -------------------> V²⁺ and CO₃²⁻

Cr₂(SO₄)₃ -------------> Cr³⁺ and SO₄²⁻

(NH₄)₂S ----------------> NH₄⁺ and S²⁻

Explanation:

Within ionic compounds, the cation is listed first, followed by the anion. Some of the ions are polyatomic, meaning they are covalently bonded to other elements. Polyatomic ions always have a specific charge.

All of these ionic compounds have an overall charge of 0. As such, the charges of the cations and anions must balance out. In order to do so, there are some compounds which have more than one atom of each ion.

2.) CrO₂

------> Oxygen (O) always forms the anion, O²⁻.

------> Therefore, if there are 2 oxygen anions, the chromium (Cr) must have the cationic form of Cr⁴⁺.

------> +4 + (-2) + (-2) = 0

3.) VCO₃

------> Carbonate (CO₃), a polyatomic ion, always has the state CO₃²⁻.

------> If there is only one atom of each ion, the charges must perfectly balance, making vanadium (V) be the cation V²⁺.

------> +2 + (-2) = 0

4.) Cr₂(SO₄)₃

------> Sulfate (SO₄), a polyatomic ion, always has the state SO₄²⁻.

-------> The only way the charges could balance out is if the chromium (Cr) is in the cationic form Cr³⁺.

------> +3 + 3 + (-2) + (-2) + (-2) = 0

5.) (NH₄)₂S

------> Ammonium (NH₄), a polyatomic ion, always has the state NH₄⁺.

------> Sulfur (S) always forms the anion S²⁻.

------> +1 + 1 + (-2) = 0

3 0

2 years ago

By what factor will the kinetic energy change if the speed of the baseball is decreased to 54.8 mi/h? Express your answer as an

Serggg [28]

Answer:

The Kinetic Energy is approximately 3 times decreased

Explanation:

A baseball weighs 5.13 oz.

a)What is the kinetic energy, in joules, of this baseball when it is thrown by a major league pitcher at 95.o mi/h?

b) By what factor will the kinetic energy change if the speed of the baseball is decreased to 54.8 mi/h? Express your answer as an integer.

Kinetic Energy (KE)=0.5×mass×velocity ^ 2

Kinetic Energy (KE)=0.5×mass × velocity ^ 2

Joules = kg×m^2/s^2

1 mile = 1609.344 meters

1 hour = 3600 sec

1 Oz = 28.34952 g = 0.02834952 kg

a) KE=0.5×m×v^2

=0.5×(5.13 oz × 0.02834952 kg/1 ounce)×(95 miles/h × 1609.344 m/1 mile × 1 hr/3600 s)^2

=130.761 kg×m^2/s^2 = 130.761 Joules

b) KE=0.5×m×v^2

=0.5×(5.13 oz × 0.02834952 kg/1 ounce)×(54.8 miles/h × 1609.344 m/1 mile × 1 hr/3600 s)^2

=43.51028 kg×m^2/s^2 = 43.51028 Joules

= 130.761 / 43.51028 = 3.00528,

As such the Kinetic Energy is approximately 3 times decreased

4 0

4 years ago

Explain how energy causes changes to earths surface

dlinn [17]

Answer:

Explanation:

The absorbed sunlight drives photosynthesis, fuels evaporation, melts snow and ice, and warms the Earth system. Solar power drives Earth's climate. Energy from the Sun heats the surface, warms the atmosphere, and powers the ocean currents.

7 0

2 years ago