(true or false) the electron structure of an atom is determined by direct observation using x-rays.

Conserving mass in a chemical reaction means the atoms of each type should be the same on both the reactant and the product side.

Further explanation:

Balanced chemical reaction:

The chemical reaction that contains an equal number of atoms of the different elements in the reactant as well as in the product side is known as a balanced chemical reaction. The chemical equation is required to be balanced to follow the Law of conservation of mass.

Law of conservation of mass:

According to this law, the mass of an isolated system can neither be created nor be destroyed in any chemical reaction. The mass of reactants and the products should be equal in accordance with this law. In other words, the number of atoms of each type should be same on both sides of the chemical reaction. The reactant is the substance that undergoes a change in itself in a chemical reaction whereas the product is the one that is formed as a result of the chemical reaction.

For example, the balanced chemical reaction between [tex]{{\text{P}}_{\text{4}}}[/tex] and [tex]{\text{C}}{{\text{l}}_{\text{2}}}[/tex] occurs as follows:

[tex]{{\text{P}}_4} + 10{\text{C}}{{\text{l}}_2} \to 4{\text{PC}}{{\text{l}}_5}[/tex]

Here,

[tex]{{\text{P}}_{\text{4}}}[/tex] and [tex]{\text{C}}{{\text{l}}_{\text{2}}}[/tex] are the reactants.

[tex]{\text{PC}}{{\text{l}}_5}[/tex] is the product.

In the above reaction, the number of potassium atoms on both reactant and product side is 4 while the number of chlorine atoms on both sides is 20. So Law of conservation of mass is followed.

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Answer details:

Grade: High School

Subject: Chemistry

Chapter: Basic concepts of chemistry

Keywords: balanced chemical reaction, law of conservation of mass, reactant, product, P4, Cl2, PCl5, 10 Cl2, 4 PCl5, atoms, same.

Adding hot cocoa to water is a physical change because it involves combining substances without changing their chemical compositions.

Adding hot cocoa to hot water is considered a physical change. When you mix hot cocoa powder with hot water, the hot cocoa dissolves and the two substances combine, but this process does not result in new chemical substances being formed. Just like other physical changes such as the melting of ice or the dissolving of sugar in water, the composition of the resulting mixture is still a combination of water and cocoa particles.

In contrast, a chemical change involves a substance transforming into a new substance with a different chemical composition, as exemplified by iron rusting (Fe + O₂ → Fe₂O₃) or the burning of gasoline.

Answer:

Compounds can be broken down into simpler substances by chemical means.

Each compound is composed of two or more types of atoms

Explanation:

im doing a 50 question quiz and this is my answer

The ph of a solution that is 0.278 m in sodium formate (NaHCO₂)  and 0.222 m in formic acid (HCO₂H) is 3.84

To calculate the pH of the solution containing sodium formate (NaHCO₂) and formic acid (HCO₂H), we first need to determine the concentrations of the formate ion (HCO₂⁻) and the formic acid (HCO₂H) in the solution.

Given:

1. Since sodium formate dissociates completely in water, the concentration of formate ion (HCO₂⁻) is equal to the concentration of sodium formate

2. The formic acid (HCO₂H) will partially dissociate in water according to the equilibrium equation:

Let x be the concentration of H⁺ ions formed from the dissociation of formic acid. Therefore, at equilibrium:

3. The equilibrium constant expression for the dissociation of formic acid is given by:

Substitute the expressions in terms of x into the equation above:

4. Calculation of pH

Therefore, The ph of a solution that is 0.278 m in sodium formate (NaHCO₂)  and 0.222 m in formic acid (HCO₂H) is 3.84

Since the density of water is 1 g /mL, hence there is 100 g of H2O. So total mass is:

m = 100 g + 5 g = 105 g

=> The heat of reaction can be calculated using the formula:

δhrxn = m C ΔT

where m is mass, C is heap capacity and ΔT is change in temperature = negative since there is a decrease

δhrxn = 105 g * 4.18 J/g°C * (-2.30°C)

δhrxn = -1,009.47 J

=> However this is still in units of J, so calculate the number of moles of NaCl.

moles NaCl = 5 g / (58.44 g / mol)

moles NaCl = 0.0856 mol

=> So the heat of reaction per mole is:

δhrxn = -1,009.47 J / 0.0856 mol

δhrxn = -11,798.69 J/mol = -11.8 kJ/mol

Fluorine and Nitrogen are both non-metals which posses non polar covalent bonds. BaO on the other hand is a combination of a metal (Ba) and non metal (O) hence making it an ionic bond. So in this case, only SO2 has polar covalent bond.

Answer:

SO2

Sulfur dioxide (SO2) is a substance with polar covalent bonds among the given options. It has atoms with different electronegativities, hence the unequal sharing of electrons. SO2's bent molecular shape also contributes to its overall polarity.

The substance with polar covalent bonds among N2, BaO, F2, and SO2 is SO2 (sulfur dioxide). Polar covalent bonds occur when there is an unequal sharing of electrons between atoms with different electronegativities.

Nitrogen (N2) and Fluorine (F2) are both diatomic molecules of the same element and thus have nonpolar covalent bonds because they share electrons equally. Barium oxide (BaO) is an ionic compound because it is composed of a metal and a nonmetal.

Sulfur dioxide (SO2), on the other hand, has atoms with different electronegativities which leads to an unequal sharing of electrons and the formation of polar covalent bonds. The molecule is also bent in shape, which contributes to its overall polarity.

The reason why Tin granules is mostly used or preferred than just a piece of Tin because a piece of Tin is plainly metal, in which this will be difficult in having it to be oxidized when it is exposed or in the air rather than Tin granules.

Answer:

To increase the surface area of reaction.

Explanation:

The tiny granules are used as they increase the surface-area to volume ratio. Smaller granules have a higher surface area to volume ratio. In a chemical reaction, it means that the reaction increases as there is more particle to particle reaction.

Hence the granules are preferred to solids.

Answer:

1. Quantitative

2. Qualitative

3. Qualitative

Explanation:

The region(s) of the periodic table which are made up of elements that can adopt both positive and negative oxidation numbers are the “non-metal” region. As we can see on the periodic table, the elements situated at the right side of the table have two oxidation states, one positive and the other a negative. 

The general properties of the elements to the right in the modern periodic table are low melting and boiling point, high ionization energy, high electron affinity, poor conductor, and lack of metallic luster.

The elements present on the right-hand side of the modern periodic table are nonmetals. Nonmetals are the elements that form negative ions by gaining electrons and have 4, 5, 6, or 7 electrons in their outermost shell.

Non-metals lack all metallic attributes and are good insulators of heat and electricity. They are generally gases at room temperature and sometimes liquid.

Nonmetals are high ionization energies and high electronegativity so they gain electrons when reacting with other compounds, to form covalent bonds.

Nonmetals have high electronegativities so they have a strong tendency to attract electrons. Nonmetals exist as liquids or gases therefore, they have low melting and boiling points under normal conditions.

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Answer:

Boiling point of water = 100 C. It is an intensive property.

Explanation:

Properties of matter can be broadly classified into two categories:

1) Chemical

2) Physical

Physical properties can be further classified as intensive and extensive properties

Intensive properties are properties that do not depend on the amount of matter. For example: Temperature, color, boiling point, melting point

Extensive properties are properties that  depend on the amount of matter. For example: Volume, mass, length

Water boils at a temperature of 100 C; this value is a constant irrespective of the volume (amount) of water. Hence boiling point is an intensive property.

For an electron to move from its zero or ground state to an excited state of higher energy level, of course it has to absorb energy.

Just like a person, energy must be supplied so that the person will be lively or active.

Answer:

energy must be absorbed

An electron absorb energy when change from ground state to excited state.

If an electron in an atom change from the ground state to an excited state, it must be absorb energy because with the help that energy it can move against the force of attraction of nucleus of that atom.

This energy provided to electron in order to remove the electron from outermost shell of that atom. If the electron release the energy then it comes back to its original position so we can conclude that electron absorb energy when change from ground state to excited state.

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To determine the number of atoms in 3.08 mol of pure aluminum, multiply the number of moles by Avogadro's number.

In order to determine the number of atoms in 3.08 mol of pure aluminum, we need to use Avogadro's number. Avogadro's number is a fundamental constant in chemistry that represents the number of atoms or molecules in one mole of a substance. It is approximately equal to 6.022 × 10²³ atoms/mol.

To find the number of atoms in 3.08 mol of pure aluminum, you can use the following calculation:

Number of atoms = 3.08 mol × (6.022 × 10²³ atoms/mol)

By performing this calculation, you will find the number of atoms in 3.08 mol of pure aluminum.

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Answer:

Lewis Dot Diagram

Explanation:

The correct number of neutrons in the nucleus of the second isotope of rubidium is 50.

To solve this problem, we can use the weighted average of the atomic masses of the two isotopes to find the number of neutrons in the second isotope. Let's denote the number of neutrons in the second isotope as [tex]\( n \)[/tex].

We know the following:

- The first isotope has 48 neutrons and a natural abundance of 72%.

- The calculated atomic mass of rubidium is 85.5.

- The second isotope has \( n \) neutrons and a natural abundance of [tex]\( 100\% - 72\% = 28\% \)[/tex].

The atomic mass of an isotope is calculated by adding the number of protons and neutrons in its nucleus. Since rubidium has 37 protons, the atomic mass of the first isotope is [tex]\( 37 + 48 = 85 \)[/tex].

Now, let's set up the equation for the weighted average atomic mass:

[tex]\[ 0.72 \times 85 + 0.28 \times (37 + n) = 85.5 \][/tex]

Solving for [tex]\( n \)[/tex]:

[tex]\[ 61.2 + 0.28n = 85.5 \] \[ 0.28n = 85.5 - 61.2 \] \[ 0.28n = 24.3 \] \[ n = \frac{24.3}{0.28} \] \[ n = 86.79 \][/tex]

Since the number of neutrons must be a whole number, we round to the nearest whole number:

[tex]\[ n \approx 87 \][/tex]

However, we must subtract the number of protons (37) to find the number of neutrons:

[tex]\[ n_{\text{neutrons}} = 87 - 37 \][/tex]

[tex]\[ n_{\text{neutrons}} = 50 \][/tex]

Therefore, the second isotope of rubidium contains 50 neutrons in its nucleus.

Presence of residual HCl will react with [tex]NaHCO_3[/tex], reducing its amount and thus lower the calculated percentage of [tex]NaHCO_3[/tex] in the mixture.

If a student cleaned a crucible with HCl and then added a [tex]NaHCO_3[/tex]-NaCl mixture without rinsing or drying it, this would affect the calculated percentage of [tex]NaHCO_3[/tex] in the mixture due to the reaction between the residual HCl and [tex]NaHCO_3[/tex]. Specifically, HCl is an acid which would react with [tex]NaHCO_3[/tex], a base, to produce NaCl, [tex]CO_2[/tex], and [tex]H_2O[/tex].

[tex]NaHCO_3[/tex] (s) + HCl (aq) → NaCl (aq) + [tex]CO_2[/tex] (g) + [tex]H_2O[/tex] (l)

This reaction would decrease the amount of [tex]NaHCO_3[/tex] in the crucible, leading to a lower calculated percentage of [tex]NaHCO_3[/tex] in the mixture than actually present. This is because the [tex]CO_2[/tex] produced escapes as a gas, reducing the mass that is attributed to [tex]NaHCO_3[/tex].