-K-12 Scientific Method
3/10
A(n)
simply states what will be observed and always
true, but does not explain why.

Answer:

170 mL

Explanation:

The total volume to be reported should be 170 mL.

According to the significant rule in mathematical operations, final answers are usually reported to reflect the accuracy of the least accurate number.

In this case, the least accurate of all the volumes has zero significant digits after the decimal, hence, the final answer after the mathematical operation should also have no significant digits after the decimal.

           18 + 128.7 + 23.45 = 170.15

Therefore, the total volume to be reported when significant digits are taken into account would be 170 mL.

Answer:

the volume of gas inside this balloon = 146.3 L

Explanation:

Given that:

The temperature T = 31 °C = ( 31 + 273.15 )K = 304.15 K

The air pressure P = 0.700 atm

number of moles of gas n = 4.10 moles

Gas constant = 0.0821 L atm/K/mol

The objective is to calculate the volume of the gas inside the ballon.

Using the Ideal gas equation

PV = nRT

V = nRT/P

V = (4.10×0.0821×304.15)/0.700

V = 102.3799/0.700

V = 146.257 L

V = 146.3 L

Thus, the volume of gas inside this balloon = 146.3 L

Answer:

The pH of 500 cm³, 0.2 mol/dm³, Ca(OH₂) is ≈ 13.6

Explanation:

The given parameters are;

Concentration of the calcium hydroxide, Ca(OH₂) = 0.2 mol/dm³

Volume of the calcium hydroxide, Ca(OH₂) = 500 cm³

Given that the calcium hydroxide, Ca(OH₂),  undergoes complete ionization in water, complete dissociation, we have;

Ca(OH₂)  ⇄  Ca²⁺ + 2 OH⁻

Therefore, we have;

2 moles of [OH⁻] for each mole of Ca(OH₂) which gives the concentration of  [OH⁻] as

[OH⁻] = 2 × 0.2 ≈ 0.4 mol/dm³

The pH is given by the formula

pH = 14 + ㏒₁₀ [OH⁻]

pH = 14 + ㏒₁₀ (0.4) = 14 - 0.3979 = 13.6021 ≈ 13.6

The pH of the 500 cm³ 0.2 mol/dm³ Ca(OH₂) ≈ 13.6.

Answer:

it's option D

Explanation:

The number of protons in the element C^12 (Carbon) is 6, number of electrons 12 and number of Neutrons is 6, same as the number of protons it contains

C^13 has 13 electrons, 6 protons and 7 Neutrons this one's neutron number is different from proton number because it's an isotope

Na^-1 has gained an electron so the number of electrons it has = 24 and the number of protons shown as 11 which means there are 23 - 11 = 12 Neutrons

O^-2 has gained two electrons and got 18 electrons in total, 8 protons and 8 neutrons

Answer:

The independent variable effects the dependent variable.

Explanation:

The independent variable Is what you change whereas the dependent variable would change because of that.

for example, the indipendent variable could be how much you water a plant in ml each day, and the dependent variable would be how tall each plant grown]s with that water doseage per day.

Answer:

Total energy consumed = 1,882.8 joules

Explanation:

Given:

Calories burned = 450 calories

Find:

Total energy consumed

Computation:

1 calorie = 4.184 joules

So,

450 calories = 4.184 × 450

450 calories = 1,882.8 joules

Total energy consumed = 1,882.8 joules

Answer:

The solution formed is called Barium hydroxide Ba(OH)2 and metal A is Barium

Explanation:

All basic oxides except BaO are insoluble in water

Answer:

When a chlorine atom gains an electron, its outermost principal energy level achieves an octet. In this case, the ion has the same outermost shell as the original atom, but now that shell has eight electrons in it. Once again, the octet rule has been satisfied.

Explanation:

Answer:

True

Explanation:

This is true because no chemical bonding or change was involved only mechanical mixing.

Answer:

1.the law that the properties of the elements are periodic functions of their atomic numbers. Also called Mendeleev's law. (originally) the statement that the chemical and physical properties of the elements recur periodically when the elements are arranged in the order of their atomic weights.

Explanation:

2.Mendeleev’s Periodic Law states that the properties of elements are the periodic function of their relative atomic masses. Mendeleev arranged all 63 elements; which were discovered till his time; in the order of their increasing relative atomic masses in a tabular form. It is known as Mendeleev’s Periodic Table.

Answer:

5.49

Explanation:

pH = - log[3.26 x 10-6] =5.49

Answer:

The mass of 3.491 × 10¹⁹ molecules of Cl₂  of Cl₂ is 4.11 × 10⁻³ grams

Explanation:

The number of particles in one mole of a substance id=s given by the Avogadro's number which is approximately 6.023 × 10²³ particles

Therefore, we have;

One mole of Cl₂ gas, which is a compound, contains 6.023 × 10²³ individual molecules of Cl₂

3.491 × 10¹⁹ molecules of Cl₂ is equivalent to (3.491 × 10¹⁹)/(6.023 × 10²³) = 5.796 × 10⁻⁵ moles of Cl₂

The mass of one mole of Cl₂ = 70.906 g/mol

The mass of 5.796 × 10⁻⁵ moles of Cl₂ = 70.906 × 5.796 × 10^(-5) = 4.11 × 10⁻³ grams

Therefore;

The mass of 3.491 × 10¹⁹ molecules of Cl₂  of Cl₂ = 4.11 × 10⁻³ grams.

Answer:

Here are some examples

Explanation:

NaCl

Cation = Na⁺, Anion = Cl⁻; ΔEN = |0.93 - 3.16| = 2.23

MgS

Cation = Mg²⁺, Anion = O²⁻; ΔEN = |1.31 - 3.44| = 2.53

KBr

Cation = K⁺, Anion = Br⁻; ΔEN = |0.82 - 2.96| =  2.14

CaF₂

Cation = Ca²⁺, Anion = F⁻; ΔEN = |1.00 - 3.98| = 2.98

In each case, ΔEN > 1.6, so the compound is ionic.

Answer:

88

Explanation:

The ion has a charge of 2+, therefore the number of neutrons it possess is 86+2

which equals 88

The element X having a mass number of 230 and has 86 electrons is radium and has  142 neutrons.

An atom is composed basically of electrons, protons and neutrons. In a neutral atom, the number of protons and electrons are equal. The number of neutrons is the difference between the mass number and the number of protons (atomic number).

Since we know that the ion of the element X has 86 electrons and the compound formed is XBr2, it then means that neutral X has 88 electrons.

The number of electrons in the neutral atom is the same as the number of protons or atomic number. An element can be identified by its atomic number. The element having atomic number 88 is radium.

The number of neutrons is obtained as;

Mass number - atomic number

230 - 88 = 142 neutrons

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Answer:

The answer to this question is approximately equal to 1.6 ×

[tex] 1.6 \times {10}^{23} atom \: o[/tex]

Answer:

a 1) XZ2

2) YZ

3) X2

b 1) Ionic bond

2) Ionic bond

3) covalent bond

c) ionic compounds has high melting and boiling point

ionic compounds can conduct electicity in aqueous form

covalent compounds have electrons shared between the atoms

covalent compounds have lower melting point compared to ionic compound

Answer:

(i) XZ = Potassium Sulfide [K2SO4]

(ii) YZ = Potassium Chloride [KCI]

(iii) X = Sulfur [S]

b) (i) Ionic Bond. (ii) Ionic Bond. (iii) Covalent Bond.

c) (i) Ionic compounds have high melting and boiling points.

(ii) Ionic compounds can conduct electricity in a molten state or a solution as they have ions that can move and carry charge.

(iii) Covalent compounds have low melting and boiling points.

(iv) Covalent compounds can not conduct electricity as all electrons are involved in bonding so there are no free electrons or ions to carry the charge.

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Answer:

CaF2

Explanation:

Calcium fluoride is a solid formed by the chemical combination of Calcium (Ca) and Fluorine (F). Two molecules of fluorine (F2) and one molecule of Calcium (Ca) are needed to form the Calcium Fluoride molecule.

An ionic bond is formed between the Calcium and Fluorine atoms i.e. electrons are transferred from calcium atoms to fluorine atoms. The calcium ion is a cation with formula; Ca2+ while fluorine is an anion with formula; F-. Hence, it takes two molecules of Fluorine ion (F-) to form a relatively stable and neutral molecule with 1 molecule of Calcium ion (Ca2+).

Answer:

c. 1.0 mole C5H5N and 1.5 mole C5H5NHCl

Explanation:

We can determine pH of a buffer using H-H equation:

pH = pKa + log [A⁻] / [HA]

Where [A⁻] is concentration of conjugate base and [HA] concentration of weak acid. These concentrations can be computed as moles of each species.

We need to determine pKa of both NH₃ and C₅H₅N buffers, thus:

pKb = -log Kb

NH₃ pKb = -log 1.8x10⁻⁵ = 4.74

C₅H₅N pKb = -log 1.7x10⁻⁹ = 8.77

And pKa = 14 - pKb:

NH₃ pKa = 14 - 4.74 = 9.26

C₅H₅N pKb = 14 - 8.77 = 5.23

A buffer works only under pH's between pKa-1 and pKa + 1. As pKa NH₃ buffer is 9.23 is not possible to produce a buffer with pH 5.05 for this system.

Thus, we only will compute the buffers made with C₅H₅N:

c. 1.0 mole C5H5N (Weak base) and 1.5 mole C5H5NHCl (Conjugate acid)

pH = pKa + log [A⁻] / [HA]

pH = 5.23+ log [1.0 moles] / 1.5 moles]

d. 1.5 mole C5H5N and 1.0 mole C5H5NHCl

pH = pKa + log [A⁻] / [HA]

pH = 5.23+ log [1.5 moles] / 1.0 moles]

Right solution is:

Answer:

-A molecule is the smallesr part is compound whereas a compound is the combination of two or more atoms in a fixed proportion by wiehgt.

- A glass of water is an example of compound but a small portion of water can be called molecule.

Answer:

.75 Tons

Explanation:

1 Ton is equal to 2,000 pounds

Answer:

The answer is D. Hydrochloric acid solution with a pH of 1.

Explanation:

I just took the same quiz

Hydrochloric acid solution with a pH of 1. Hence, option D is correct.

An acid is an electrolyte that hydrolyses in water to release hydrogen ions.

The lower the pH the greater the concentration of H+ ions. Hydrochloric acid with a pH of 1 is a strong acid and is highly ionised in solution.  It has the most H+ ions.

Hence, option D is correct.

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Answer:

ionic

Explanation:

In NH4Cl molecule, ionic bond is formed between NH4+ and Cl– ions, 3 covalent bonds are formed between N and three H atoms and one coordinate bond is formed between N and 1 H atom.

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Answer:

[tex]\boxed{\sf c. \ ionic}[/tex]

Explanation:

NH₄Cl is formed by an ionic bond between NH₄⁺ and Cl⁻ ions.

NH₄Cl (solid) ⇒ NH4⁺ (aqueous) + Cl⁻ (aqueous)

Answer:

the amount of fertilizer; x-axis

plant height; y-axis

Explanation:

The independent and dependent variables of Levi's experiment placed when graphed are the amount of fertilizer and the y-axis. Option B is correct.

The independent variables are those which are not dependent on other factors for their working or cannot be influenced by any other factor and the dependent variable is just the opposite of this one.

The experiment depends on the height of the plant but the fertilizer is independent of to work of the plant and fertilizer is independent and high and depends on other factors.

Therefore, Option B is correct. independent and dependent variables of Levi's experiment placed when graphed are the amount of fertilizer and the y-axis.

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Answer:

conclusion

Explanation:

it can't be a hypothesis since tests are carried out to verify so it is not a theory

an introduction to an experiment only gives the basis of what we are investigating therefore nothing has been proven and the question is still unanswered

The overall takeaway of an experiment’s results is the conclusion. Hence, option C is correct.

A hypothesis is a testable statement about the relationship between two or more variables or a proposed explanation for some observed experiment.

The overall takeaway of an experiment’s results can't be a hypothesis since tests are carried out to verify so it is not a theory

An experiment only gives an idea about the investigation therefore nothing has been proven and the question is still unanswered.

Hence, the overall takeaway of an experiment’s results is the conclusion.

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Answer:

The proportionality constant ( Henry’s constant) = 2.32 * 10^-5 M/kPa

Explanation:

Here in this question, we are concerned with calculating the proportionality constant for this gas.

Mathematically, we can get this from Henry law

From Henry law;

Concentration = Henry constant * partial pressure

Thus Henry constant = concentration/partial pressure

Henry constant = 0.00290 M/125 kPa = 2.32 * 10^-5 M/kPa

Answer:

0.8833 mole of C3H8

Explanation:

Given:

Mass of C₃H₈ (Propane) = 38.95 gram

Computation:

Molar mass of C = 12.01

Molar mass of H = 1.008

Molar mass of C₃H₈ (Propane) = 3(12.01) + 8(1.008)

Molar mass of C₃H₈ (Propane) = 36.03 + 8.064

Molar mass of C₃H₈ (Propane) = 44.094

Number of mol in 38.95 gram Propane = Mass / Molar mass

Number of mol in 38.95 gram Propane = 38.95 / 44.094

Number of mol in 38.95 gram Propane = 0.88334

Answer:

Use the Periodic Table to find molar masses.

Propane (C3H8), a common fuel, reacts with oxygen to form carbon dioxide and water according to the equation below:

C3H8 + 5O2 → 3CO2 + 4H2O

If a propane heater burns 38.95 g C3H8, it consumes

38.95 mol C3H8.

0.8830 mol C3H8.

1 mol C3H8.

44.10 mol C3H8.

Part 2

How many moles of oxygen are required to produce 37.15 g CO2?

37.15 g CO2 = 1.407 mol O2

Part 3

What mass of propane is necessary to react with the amount of oxygen calculated in the previous question?

12.41   g C3H8    

Answer:

The answer is "Option B"

Explanation:

when we react with FeCl, iron, and chloride to both the electrolysis. So, iron is charged positive ion, as well as passes to the negative, is cathode electrode. But there is a decrease in the cathode.

The equation can be defined as follows:

[tex]FeCl_2[/tex] [tex]\longrightarrow[/tex][tex]Fe + Cl_2[/tex]

In the above equation, when the iron chloride electrolysis solution, it will give the iron(II) and the chlorine. This process happens when the hydrogen chloride solution at a temperature of about 90 ° C.

Answer: D

Explanation: As Fe is positive charged while chlorine is negative charged.

(D) is correct. As iron moves to negative and it get reduce as negative electrode is cathode

Solid, Liquid, and Gas

Solid is the state in which matter maintains a fixed volume and shape; liquid is the state in which matter adapts to the shape of its container but varies only slightly in volume; and gas is the state in which matter expands to occupy the volume and shape of its container.

The states of matter are solid, liquid, and gas. Solid is the state in which matter maintains a fixed volume and shape; liquid is the state in which matter adjusts to the shape of its container but tends to vary only mildly in volume; and gas is the state in which matter expands to occupy the volume and shape of its container.

Matter would be any substance with mass and volume that occupies space.

Matter exists in three states: solid, liquid, and gas. The states of matter are solid, liquid, and gas.

Thus, above-mentioned are the three states of matter.

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Answer:

Scientists

Explanation:

Scientists because they are the one who makes hypothesis.