Please help!
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Answer:

Explanation:

11- d

12- dont know

13- c

14- d = 30

15-  b =64

16- c = 34

17-  positive= 19 protons , negative= 19electrons , neutral = 39 - 19 = 20 notrons

18- chlorine-35

because atomic mass (35.453) is close to (35)

It is difficult tp precisely date samples from after the 1940's is Nuclear bombs contaminated the samples with more radioactivity.

We use radioactive method to date the samples by using various radioisotopes and it gives a high degree of accuracy but this radioactive method may not work in future because of Nuclear bombs , nuclear reactors test started changing environment and this will lead to the difficulties in dating sample precisely.

Radiocarbon dating or carbon - 14 dating uses natural occurring radioisotope carbon - 14,It is used to determine the age of object from bones to plant fibers and wood, by the radiocarbon properties.

Thus , It is difficult tp precisely date samples from after the 1940's is Nuclear bombs contaminated the samples with more radioactivity.

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Answer: I believe its ice melting

Explanation: it would be ice melting because it can turn back into ice by itself with out any human doing anything to it.

An analytical chemist measures the amount of Elements and in four samples of an unknown Substance ;

as per the samples  :

we have mass % of

[tex]E_1[/tex] in Sample 1 = 8.2g x 100/ 8.29 +18.99

= 30%

mass % [tex]E_1[/tex] in sample2 = 6.19 x 100/ 6.1 g +13.9 g  

=30%

Similasly mass % of [tex]E_1[/tex]in sample 3 and sample are also 30%

Hence mass % [tex]E_2[/tex] in all samples are  70%

:. X is a pure substance

mass of sample x = 10.0g

mass of Element El = 30% of x

= 30 x 100g/ 100

= 3.og

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Answer:

866.142 inches

Explanation:

By formula

The average atomic mass of naturally occurring strontium which consists of four isotopes, Sr-84, Sr-86, Sr-87, and Sr-88 is 87.1 amu.

To determine average atomic mass,

we take average of weight of all of the isotopes of that element.

Molecular weight of -

Sr-84 = 83.9 amu

Sr-86 = 85.9 amu

Sr-87 = 86.9 amu

Sr-88 = 87.9 amu

Average = 83.9 + 85.9 + 86.9 + 87.9 = 86.15

                                     4

We'll see the abundance of each isotope of strontium. Since the most abundant isotope of strontium is Sr-88 with 82.6% abundance. Therefore, the average atomic mass of strontium is closest to the mass of Sr-88, and the other isotopes are less than this mass.

Hence, the atomic mass of strontium is, 87.1 amu.

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Taking into account the reaction stoichiometry, 120.615 kg of HNO₃ are consumed to produce 112 kg Ca(H₂PO₄)₂.

In first place, the balanced reaction is:

Ca₃(H₂PO₄)₂ + 4 HNO₃  → Ca(H₂PO₄)₂ + 2 Ca(NO₃)₂

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:

The molar mass of the compounds is:

Then, by reaction stoichiometry, the following mass quantities of each compound participate in the reaction (being 1000 g= 1 kg):

The following rule of three can be applied: If by reaction stoichiometry 0.234 kg of Ca(H₂PO₄)₂ is produced from 0.252 kg of HNO₃, 112 kg of Ca(H₂PO₄)₂ is produced from how much mass of HNO₃?

mass of HNO₃= (112 kg of Ca(H₂PO₄)₂× 0.252 kg of HNO₃)÷ 0.234 kg of Ca(H₂PO₄)₂

mass of HNO₃= 120.615 kg

Finally, 120.615 kg of HNO₃ are consumed to produce 112 kg Ca(H₂PO₄)₂.

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Answer:

0.0996 M (3 s.f.)

Explanation:

Molarity is the number of moles per litre.

Let's find the number of moles of sucrose.

[tex]\boxed{\text{Moles= Mass}\div\text{Mr}}[/tex] , where Mr is the molecular weight of the compound.

[tex]\text{Mr of C}_{12}\text{H}_{22}\text{O}_{11}[/tex]

= 12(12)+22(1)+11(16)

= 342

Moles of sucrose

= 143 ÷342

= 0.41813 mol (3 s.f.)

This means that in 4.20L of solution, we have approximately 0.41813 moles of sucrose. We can now calculate the amount of sucrose in 1L of solution.

Molarity

= 0.41813 ÷4.2

= 0.099555 mol/L (5 s.f.)

= 0.0996 M (3 s.f.)

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Answer:

Which statement describes a step in the formation of an ionic bond? An attraction occurs between two ions that have the same charge.

Explanation:

If the concentration inside the cell is 5% and the concentration outside the cell is 6%, this solution will be hypertonic.

If the concentration inside the cell is 3% and the concentration outside the cell is 1%, this solution will be hypotonic.

Hypertonic solution is a solution that contains more dissolved particles (such as salt and other electrolytes) than is found in normal cells and blood.

A solution will be hypertonic to a cell if the outside concentration is higher than that inside the cell, and the solutes cannot cross the membrane.

Hypotonic solution is a solution that contains fewer dissolved particles (such as salt and other electrolytes) than is found in normal cells and blood.

A solution will be hypotonic to a cell if the outside concentration is lower than that inside the cell, and the solutes can cross the membrane.

Thus, if the concentration inside the cell is 5% and the concentration outside the cell is 6%, this solution will be hypertonic.

if the concentration inside the cell is 3% and the concentration outside the cell is 1%, this solution will be hypotonic.

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Since it contains a phenol group, acetaminophen will give a positive phenol test when ferric chloride is added. Salicylic acid remains unreacted and causes a color change when it reacts with ferric chloride.

Phenol is primarily used in the manufacture of phenolic resins as well as nylon and other synthetic fibers.

It is also used as a disinfectant and antiseptic, as well as in medicinal preparations such as mouthwash and sore throat lozenges.

Acetaminophen will give a positive phenol test when ferric chloride is added because it contains a phenol group. When salicylic acid reacts with ferric chloride, it remains unreacted and causes a color change.

Thus, it can be concluded that yes, positive phenol test can be taken in case of acetaminophen.

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The balanced dissociation equation of the ionic compound ZnCl₂ is given below:

A dissociation equation of  a chemical reaction is a n equation which shows the products formed when an ionic substance is dissolved in an aqueous solution to produce ions.

A dissociation reaction results in the formation of ions and occurs only in ionic compounds

The dissociation of the ionic compound ZnCl₂ is shown below:

From the equation above, the ionic compound zinc chloride is dissolved in water. The dissolution of the compound inn water results in the free dissociation or separation of the ions present in the crystal structure of the compound.

The compound dissociates to produce two moles of chloride ions and one mole of zinc (ii) ions. This is because the charge on the zinc ion is +2 while that on the chloride ion is -1.

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The energy that is transferred by  0.432 mol carbon is 200.79 kJ.

We know that the heat of reaction refers to the heat that was evolved or absorbed when reactants combine to form a product. The heat of reaction is positive when heat is absorbed and it is negative when heat is evolved.

Given the fact that we have the reaction; [tex]CaO(s)+3C(s) -------- > CaC_{2} (s) + CO (g)[/tex]→Ca[tex]C_{2}[/tex](s)+CO(g) ΔH=464.8kJ We are now required to obtain the quantity of energy, in kJ, transferred when 0.432 mol carbon reacts with CaO(s).

Given that;

1 mole of CaO transfers 464.8kJ of energy

0.432 mol carbon transfers 0.432 mol * 464.8kJ /1 mole

= 200.79 kJ

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Answer:

k=0.0224 M/s

Explanation:

Give me Brainliest if that helped! :)

The rate constant of the reaction is 0.0224 m/s. the rate constant is denoted by symbol k. The velocity and direction of a chemical reaction are quantified in chemical kinetics by the reaction rate constant, or reaction rate coefficient, k.

The proportionality constant in the equation that defines the link between the rate of a chemical reaction and the concentrations of the reacting chemicals is known as the rate constant, also known as the specific rate constant.

The rate constant provides insight into the variables that affect a reaction's rate. The dependence of the molar concentration of the reactants on the rate of reaction may be determined by knowing the rate constant.

The rate constant provides insight into the variables that affect a reaction's rate. The dependence of the molar concentration of the reactants on the rate of reaction may be determined by knowing the rate constant.

Thus, option 2 is correct.

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Answer:

A. Add 40 and 44

Explanation:

mass number = protons + neutrons

protons = electrons

so mass number = 40 + 44

The atoms that are the same element are atoms 1 and 2, because they have the same number of protons (option D).

Element is one of the simplest chemical substances that cannot be decomposed in a chemical reaction or by any chemical means and made up of atoms all having the same number of protons.

The atoms of an element have the same number of protons, which is the atomic number.

According to the table given above, three atoms and their respective proton, electron and neutron number are given.

It can be said that atoms 1 and 2 are of the same element, because they have the same number of protons.

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The gold will fill up 5.00 cm³of space if the density of gold is 19.3 g/cm³. Then the amount of gold filled in 5.00 cm³ of space is 96.5g.

Density is defined as the measurement of how tightly the material is packed together.

Density is defined as mass/volume.

The SI unit of density is gram/cubic centimeter.

Density can be expressed as

Density = mass/volume

As density is given as 19.3 gm/cm³ and volume is 5.00 cm³, then the mass can be calculated as

Mass = density x volume

         = 19.3 x 5.00 = 96.5g

Thus, the amount of gold filled in 5.00 cm³ of space is 96.5g.

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The statements  'The precision is a measure of the spread of expected values for a given measurement .'  does not accurately describe the precision of a measurement .

Precision refers to how close measurements of the same item are to each other . Precision is independent of accuracy . That means it is possible to be very precise but not very accurate, and it is also possible to be accurate without being precise . The best quality scientific observations are both accurate and precise .

It is also define in one term as the quality or state of being precise .

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The option that best describes the outer shell of the atoms in Group 17 is they have 7 electrons.

Group 17 elements such as chlorine, fluorine, etc have low bond dissociation energy due to their small atomic radius.

Basic characteristics include:

Thus, the option that best describes the outer shell of the atoms in Group 17 is they have 7 electrons.

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The final temperature of an 18.0 g aluminum sample if it is initially at 22.0 C and it absorbs 48.0 calories of heat energy is 34.7°C.

The temperature of a substance can be calculated using the following formula:

Q = mc∆T

Where;

According to this question, an 18.0 g aluminum sample is initially at 22.0 C and it absorbs 48.0 calories of heat energy. The final temperature can be calculated as follows:

48 = 18 × 0.210 × {X - 22}

48 = 3.78x - 83.16

3.78x = 131.16

X = 34.7°C

Therefore, the final temperature of an 18.0 g aluminum sample if it is initially at 22.0 C and it absorbs 48.0 calories of heat energy is 34.7°C.

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The number of atoms in 1.49×10³ g sample of strontium is 1.02×10²⁵ atoms

1 mole of strontium = 6.02×10²³ atoms

But

1 mole of strontium = 87.62 g

Thus, we can say that:

87.62 g of strontium = 6.02×10²³ atoms

We can determine the number of atoms in 1.49×10³ g of strontium as illustrated below:

87.62 g of strontium = 6.02×10²³ atoms

Therefore,

1.49×10³ g of strontium = (1.49×10³ g × 6.02×10²³ atoms) / 87.62 g

1.49×10³ g of strontium = 1.02×10²⁵ atoms

Thus, 1.02×10²⁵ atoms are present in 1.49×10³ g of strontium

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A 51.0 mL portion of a 1.60 M solution is diluted to a volume of 288 ml. A 155 mL portion of that solution is diluted by adding 147 mL of water, the final concentration is 0.140 M.

so, in this dilution occurs two times:

Initial concentration is C1 = 1.60 M

concentration after first dilution C2 = ?

volume V1 = 51.0 ml

volume V2 = 288ml

the dilution formula :

C1 × V1 = C2 × V2

C2 = (C1 × V1 ) / V2

     =  ( 1.60 × 51.0 ) / 288

     =  0.283 M

Now, for the second dilution :

V2 = 144 mL

V3 = 147mL + 144mL= 291 mL ( diluted by adding  water)

C2 × V2 = C3 × V3

C3 = (C2 × V2) / V3

     =  ( 0.283 × 144 ) / 291

     =  0.140 M

Thus, A 51.0 mL portion of 1.60 M solution is diluted to a volume of 288 ml. A 155 mL portion of that solution is diluted by adding 147 mL of water, the final concentration is 0.140 M.

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Explanation:

NH₃+NO=N₂+H₂O;

NH₃+NO=N₂+6H₂O;

NH₃+6NO=N₂+6H₂O;

4NH₃+6NO=N₂+6H₂O;

4NH₃+6NO=5N₂+6H₂O.

Answer:

because it is good conductor of electricity

Answer:

3.01 x 10²⁴ atoms Mn

Explanation:

To find the number of manganese (Mn) atoms, you need multiply the given mole value by Avogadro's Number. Avogadro's number is a ratio which represents the number of atoms per every 1 mole. It is important to arrange the ratio in a way that allows for the cancellation of units (moles should be in the denominator to cancel the units of the given value). The final answer should have 3 sig figs like the given value (5.00 = 3 sig figs).

Avogadro's Number:

6.022 x 10²³ atoms = 1 mole

5.00 moles Mn           6.022 x 10²³ atoms
-------------------------  x  --------------------------------  = 3.01 x 10²⁴ atoms Mn
                                              1 mole

The graphite is brittle in nature and this property makes the graphite to be break very easily or to make the graphite weak.

Actually the graphite is naturally very brittle compound and the graphite can not be used as a material structure on its own due to its sheer planes.

The fact that why graphite is brittle is that the carbon atoms in the graphite are only bounded by the three strong covalent bonds  in a two-dimensional 'layer lattice'.

The bonds inside the atoms of the carbon which is present in the layers of the graphite maybe strong but  but the bonds that are formed by carbon atoms between layers are very weak, so that's why the graphite can be broken easily.

So we can conclude that the graphite is brittle in nature and this property makes the graphite to be break very easily or to make the graphite weak.

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