Choose all the right answers. Select three options.

The structures common to all protozoa are:


chloroplast
cytoplasm
cell membrane
cilia
cell wall
nucleus

The rate of a reflection decreases when the temperature increases

This goes to say that the rate of reflection will go down more whenever there is an increase in temperature

Reflection can simply be defined as the the throwing back by a body of light without absorbing it.

reflection of

In conclusion, the rate of a reflection decreases when the temperature increases

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The mass of melted gold to release the energy would be  3, 688. 8 Kg

The formula for quantity of energy is given thus;

Q = n × HF

Where n represents number of moles

HF  represents  heat of fusion

To find the number of moles, we have

235.0 = n × 12.550

number of moles = [tex]\frac{235}{12. 550}[/tex] = 18. 725 moles

Note that molar mass of Gold is 197g/ mol

Let's note that;

Number of moles = mass/ molar mass

Mass = number of moles × molar mass

Mass = 18. 725 × 197

Mass = 3, 688. 8 Kg

Thus, the mass of melted gold to release the energy would be  3, 688. 8 Kg

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The molecule  is composed of two nitrogen atoms above and below the plane of four carbon atoms to which four hydrogen atoms are attached.

The Lewis structure shows the arrangement of electrons in atoms of molecules. The molecule C4H4N2 is called pyrazine. It is composed of two nitrogen atoms above and below the plane of four carbon atoms to which four hydrogen atoms are attached.

The structure of the molecule C4H4N2  in which formal charges are minimized is shown in the image attached to this answer.

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The name of Pb(NO3)2 of is Lead II trioxonitrate V

The bond which exist in is Lead II trioxonitrate V ( Pb(NO3)2 ) are both ionic and covalent bond

A compound is a substance which contains two or more elements chemically combined together

So therefore, the name of Pb(NO3)2 of is Lead II trioxonitrate V

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According to the research, the correct option is 3, Igneous rocks are those formed from a molten product from volcanic activity.

They are rocks of high resistance, isotropy, brittleness and density that are created from the cooling and solidification of the magma, whether fragmented or compact, that form at erupting volcanoes, that is, this substance, made up of molten rocks and other elements, is found inside the planet.

When the cooling process takes place superficially and quickly, extrusive igneous rocks are produced, among which are obsidian and basalt, they usually appear after the eruption of a volcano, since the ejected lava solidifies.

Therefore, we can conclude that according to the research, the correct option is 3, Igneous rocks are those formed from a molten product from volcanic activity.

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The volume of potassium iodide used will be 0.087 L or 87 mL

The equation of the reaction goes thus: [tex]Pb(NO_3)_2(aq) + 2KI --- > PbI_2(s) + 2KNO_3(aq)[/tex]

The mole ratio of the 2 reactants is 1:2.

Mole of 9.42 g [tex]Pb(NO_3)_2[/tex] = 9.42/331.2 = 0.02844 mol

Equivalent mole of KI = 0.02844 x 2 = 0.05688 mol

Volume of 0.05688 mol, 0.655 mol/L KI = 0.05688/0.655 = 0.087 L or 87 mL

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Answer:

D.) their valence electrons are free-roaming

Explanation:

Metals tend to arrange themselves in crystalline structures once they form metallic bonds. The electrons around the positive nuclei are delocalized, and thus freely float within the structure. This is unique to metallic bonding.

Answer:

49.8 g C₆H₅Br

Explanation:

The theoretical yield is the maximum calculated amount of product that can be made from a reaction. To find the theoretical yield, you need to (1) determine the chemical reaction which is taking place, then (2) calculate the molar masses of the relevant reactants and product, then (3) convert grams of each reactant to grams of bromobenzene (using molar masses and mole-to-mole ratio from reaction coefficients), and then (4) determine the limiting reagent and the theoretical yield.

(Step 1)

Bromine = Br₂

Benzene = C₆H₆

Bromobenzene = C₆H₅Br

The balanced equation:

Br₂ + 2 C₆H₆ ----> 2 C₆H₅Br + H₂

(Step 2)

Molar Mass (Br₂): 2(79.904 g/mol)

Molar Mass (Br₂): 159.808 g/mol

Molar Mass (C₆H₆): 6(12.011 g/mol) + 6(1.008 g/mol)

Molar Mass (C₆H₆): 78.114 g/mol

Molar Mass (C₆H₅Br): 6(12.011 g/mol) + 5(1.008 g/mol) + 79.904 g/mol

Molar Mass (C₆H₅Br): 157.01 g/mol

(Step 3)

52.3 g Br₂           1 mole             2 moles C₆H₅Br         157.01 g
----------------- x  ------------------  x  -------------------------  x  ---------------  =
                          159.808 g              1 mole Br₂               1 mole

=  103 g C₆H₅Br

24.8 g C₆H₆         1 mole            2 moles C₆H₅Br          157.01 g
-------------------  x  ---------------  x  --------------------------  x  ---------------  =
                             78.114 g           2 moles C₆H₆             1 mole

=  49.8 g C₆H₅Br

(Step 4)

Because C₆H₆ produces a smaller amount of product than Br₂, it must be the limiting reagent. This means that it will run out before all of the Br₂ is used up. Therefore, the actual theoretical yield of C₆H₅Br is 49.8 grams.

Reasoning includes one or more scientific principles in this context.

This involves the thought about something in a sensible and logical manner due to one or more scientific principles being applied.

It is very important to the claim and evidence as it helps ascertain their validity in science.

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Answer:

See-saw

Explanation:

To determine the molecular shape of BrF₄⁺, you need to

1.) Calculate the valence electrons of BrF₄⁺

    ----> Add the valence electrons of each individual atom

    ----> Take the positive charge into account (subtract 1 electron)

2.) Draw the Lewis Dot diagram of BrF₄⁺

    ----> Each bond has 2 electrons

    ----> Bromine can have an expanded octet

3.) Determine the molecular shape of BrF₄⁺

The equation that conforms with the particle model is 4C + 6O2 ----> 4CO2 + 2O2.

The term chemical reaction has to do with the combination of substances to give products. We know that reactants and products must follow the law of conservation of mass.

Hence, the equation that conforms with the particle model is 4C + 6O2 ----> 4CO2 + 2O2.

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The melting points of sugar and salt are above 20°C.

The melting points of substances refer to the temperature at which solid substances gain enough energy to become liquids.

The room temperature is approximately 20°C. At this temperature, sugar and salt are solids. This means that the melting temperature of both substances is above 20°C.

More specifically, sugar will melt around 180 °C while salt will melt at a temperature slightly above 800 °C.

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Conversion factors are useful in solving problems in which a given measurement must be expressed in some other units of measure.

Conversion factors are helpful in solving issues where one unit of measurement needs to be expressed in another. In general, a measurement's numerical value changes when it is multiplied by a conversion factor, while the quantity being measured's real size stays the same.
A conversion factor is a number that is used to multiply or divide one set of units into another. If a conversion is required, it must be done using the correct conversion factor to get an identical value. For instance, 12 inches equals one foot when converting between inches and feet.

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Considering the definition of percentage by mass, the mass percentage of CaCO₃ is 68.59%.

The percentage by mass expresses the concentration and indicates the amount of mass of solute present in 100 grams of solution.

In other words, the percentage by mass of a component of the solution is defined as the ratio of the mass of the solute to the mass of the solution, expressed as a percentage.

The percentage by mass is calculated as the mass of the solute divided by the mass of the solution, the result of which is multiplied by 100 to give a percentage. This is:

[tex]mass percentage=\frac{mass of solute}{mass of solution}x100[/tex]

In this case, you know:

Replacing in the definition of mass percentage:

[tex]mass percentage=\frac{2.62 grams}{3.82 grams}x100[/tex]

mass percentage= 68.59 %

Finally, the mass percentage of CaCO₃ is 68.59%.

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Answer:

1

Explanation:

The empirical formula describes the simplest whole number ratio of each type of atom in a compound. To find this formula, you need to (1) convert grams of each element to moles (via their atomic masses) and then (2) find the ratio of each element (by dividing each molar value by the smallest mole value).

(Step 1)

Atomic Mass (Zn): 65.380 g/mol

Atomic Mass (C): 12.011 g/mol

Atomic Mass (O): 15.998 g/mol

10.40 grams Zn              1 mole
------------------------  x  ------------------------  =  0.159 moles Zn
                                   65.380 grams

1.92 grams C               1 mole
---------------------  x  -----------------------  =  0.160 moles C
                                 12.011 grams

7.68 grams O               1 mole
----------------------  x  ------------------------  =  0.480 moles O
                                 15.998 grams

(Step 2)

0.159 moles Zn / 0.159  =  1 atom Zn

0.160 moles C / 0.159  =  1 atom C

0.480 moles O / 0.159  =  3 atom O

The empirical formula is Zn₁C₁O₃. Therefore, the value that should be in the space is 1.

The balanced chemical equation for the reaction is:

2NaOH(aq) + FeCl₂(aq) --> 2NaCl(aq) + Fe(OH)₂(s)

Chemical equations are representations of chemical reactions using symbols and formula of the reactants and products.

The reactants are located on the left side while the products are located on the right side.

Reactants —> Products

The balancing of chemical equations follows the law of conservation of matter which states that matter can neither be created nor destroyed during a chemical reaction but can be transferred from one form to another.

Sodium hydroxide => NaOH

Iron (II) chloride => FeCl₂

2NaOH(aq) + FeCl₂(aq) --> 2NaCl(aq) + Fe(OH)₂(s)

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Enslaved African is best described as the condition which involved transporting people against their will to work on large farms without pay.

This is referred to a situation in which an individual is owned by another. Slaves were moved from Africa against their will to work on large farms.

They weren't given any pay and worked under hard conditions thereby making option B the correct choice.

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Answer:

1.17 moles H₂SO₄

Explanation:

To find the moles H₂SO₄, you need to multiply the given value by the mole-to-mole ratio. This ratio is made up of the coefficients of the relevant molecules from the balanced chemical equation. It is important to arrange the ratio in a way that allows for the cancellation of units.

S + 6 HNO₃ ------> 1 H₂SO₄ + 6 NO₂ + 2 H₂O
     ^                      ^

7 moles HNO₃          1 mole H₂SO₄
-----------------------  x  ------------------------  =  1.17 moles H₂SO₄
                                  6 moles HNO₃

The proper explanations to the observation are;

A redox reaction is one in which a specie is oxidized while the other specie is reduced. In the first observation, the color of the solution turned blue and in the second observation, shiny hair like crystals deposited on the copper strip.

Hence;

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Answer:

1.) Yes, Cs₂S

2.) Yes, MgF₂

3.) Yes, MgS

4.) No

Explanation:

Nonmetals are located on the right side of the periodic table in the p-block. It is safe to assume that all the other elements are metals.

Ionic bonds form between a metal and nonmetal. When determining the empirical formula, the cation (the element losing electrons) is written before the anion (the element gaining electrons). The charges can be balanced by modifying the quantity of element.

1.) Cs₂S

  -----> Cesium = metal and Sulfur = nonmetal

  -----> Cesium = Cs⁺

  -----> Sulfur = S²⁻

2.) MgF₂

  -----> Magnesium = metal and Fluorine = nonmetal

  -----> Magnesium = Mg²⁺

  -----> Fluorine = F⁻

3.) MgS

  -----> Magnesium = metal and Sulfur = nonmetal

  -----> Magnesium = Mg²⁺

  -----> Sulfur = S²⁻

4.) Both cesium and strontium are metals

The freezing point of the sucrose solution is -0.435°C.

The freezing point of the solution is determined from the freezing point depression formula below:

Kf(H₂O) = 1.86 Cm

m is molality of solution = moles of solute/mass of solvent

moles of sucrose = 8.0/342.3 = 0.0233 moles

m = 0.0233/0.1 = 0.233 molal

ΔT = 0.233 m * 1.86°C/m.

ΔT = 0.435 °C.

Freezing point of sucrose solution = 0°C - 0.435°C

Freezing point of sucrose solution  = -0.435°C.

In conclusion, the freezing point of sucrose solution is determined from the freezing point depression.

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33.33 grams of CH4 would be formed from 25 g C.

C + 2H2 → CH4

from given reaction we can say that ,

2 moles of hydrogen is required for 1 mole of carbon and these will react to form 1 mole of methane.

atomic mass of Carbon = 12 gm

Molecular mass of H2 = 2(H)

                                  = 2(1)

                                  =2gm

moles = molecular mass / given mass

for C,

if 12 gm = 1 mole

then 25 gm = ? mole

           =2.083 moles

1 mole of C will produce 1 moles of CH4

so, 2.083 moles of C also will produce 2.083 moles moles of CH4

molecular weight of methane= C+4(H)

                                             = 12+4(1)

                                             = 16 gm

amount of methane produced= moles × molecular mass

                                              =2.083× 16

                                              = 33.33 gm

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Please get it cleared and stored into your cerebrum that a cation is formed when a neutral atom loses one or more electrons from its valence electron shell.

However too, on other hand an anion is formed when a neutral atom gains one or more electrons in its outermost electron shell.

A cation means a positive ion

An anion means a negative ion

Electronegativity is one of physical periodicity and property of elements that describes the tendency of an atom to attract electrons toward itself.

Generally, electronegativity of an atoms of elements in a particular trend is affected by both its atomic number and the distance that its valence electrons reside from the charged nuclei.

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Answer:

4. -ol

5. cyclic ketone

Explanation:

biology stuff

sorry it's hard to explain

Taking into account the definition of pH and pOH, the pH of the solution is 12.

pH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance.

The pH is defined as the negative base 10 logarithm of the activity of hydrogen ions, that is, the concentration of hydrogen ions or H₃O⁺:

pH= - log [H⁺]= - log [H₃O⁺]

Similarly, pOH is a measure of hydroxyl ions in a solution and is expressed as the logarithm of the concentration of OH⁻ ions, with the sign changed:

pOH= - log [OH⁻]

The following relationship can be established between pH and pOH:

pOH + pH= 14

A solution had a hydroxide ion concentration of 1×10⁻² M. In other words [OH⁻]= 1×10⁻² M.

Replacing in the definition of pOH, it is calculated as:

pOH= - log (1×10⁻² M)

Solving;

pOH= 2

Replacing in the relationship established between pH and pOH, the pH can be calculated as:

pH + 2= 14

Solving:

pH= 14 - 2

pH= 12

In summary, the pH of the solution is 12.

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The pH of a 0.0100 M sodium benzoate solution with a Kb of 1.5 × 10-¹⁰ is 5.91 (option B).

The pH of a solution in chemistry refers to the notation expressing the acidity or alkalinity of a solution.

The pH is measured on a logarithmic scale of which 7 is neutral, lower values are more acid and higher values more alkaline.

The pH of a solution can be calculated using the following formula;

pH = - log {H+}

pH = - log {0.0100}

pH = 2

Therefore, the pH of a 0.0100 M sodium benzoate solution with a Kb of 1.5 × 10-¹⁰ is 5.91.

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The correct statement regarding the limiting reactant for the reaction between 4 moles of iron and 3 moles of oxygen is: They are both equal. (Option A)

We'll begin by writing the balanced equation for the reaction between iron and oxygen. This is given below:

4Fe + 3O₂ --> 2Fe₂O₃

SUMMARY

From the balanced equation above,

4 moles of Fe reacted with 3 moles of O₂

The limiting reactant is the reactant that is consumed completly in a chemical reaction.

The limiting reactant can be obtain as illustrated below:

From the balanced equation above,

4 moles of Fe reacted with 3 moles of O₂

From the illustration above, we can see that 3 moles of Fe required 4 moles of O₂ for complete reaction.

Thus, Fe and O₂ are both the limiting reactant.

Therefore, we can conclude that Fe and O₂ are equal

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The sign of the entropy change, ΔS, for the following processes include:

What is Entropy?

This is referred to the degree of randomness or disorderliness of a system and is denoted as S.

Entropy change is usually positive when solid or liquid reactant is converted into gas product and vice versa.

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