Which four practices are examples of how humans use science?
A. Making decisions that help humans survive
OB. Developing technologies that help humans thrive
C. Developing explanations based on facts
D. Imagining entertaining stories that explain observations
O E. Gathering facts that explain natural events

Answer:

A ; 20g of water has the least number of molecules

Explanation:

Here, we want to know which of the options represent the least number of molecules;

To calculate this, we are going to first calculate the number of moles using the formula below;

Number of moles = mass/molar mass

Then from the number of moles, we can calculate the number of molecules by multiplying the number of moles by 6.02 * 10^23 molecules

Let’s proceed;

a. That will be 20/18.02 = 1.1099 moles

1.1099 * 6.02 * 10^23 = 6.68 * 10^23 molecules

b. That will be 77/16.06 = 4.8 moles

4.8 * 6.02 * 10^23 = 2.89 * 10*24 molecules

c. That will be 68/42.09 = 1.62 moles

1.62 * 6.02 * 10^23 = 9.73 * 10^23 molecules

d. That will be 100/44.02 = 2.27 moles

2.27 * 6.02 * 10^23 = 1.37 * 10^24 molecules

e. That will be = 84/20.01 = 4.2 moles

4.2 * 6.02 * 10^23 = 2.53 * 10^24 molecules

From all the values obtained, the lowest is 20g of water

Explanation:

n=given mass ÷molar mass

make given mass become the subject of the formula by

multiplying the molar mass on both sides of the equation.

n=0.473mol

given mass=??

molar mass=48

therefore,given mass=n×molar mass

=0.473×48

=22.704grams

mass in grams is 22.704grams

The mass (in grams) of 0.473 mol of titanium is 22.6 grams.

We have some specific amount of moles of titanium.

We have to calculate the mass of given sample of titanium.

Titanium is a chemical element with the symbol Ti and atomic number 22. It is found in nature only as an oxide.

According to the question -

Moles of titanium - 0.473 moles.

Mass of 0.473 moles of titanium =

0.473 moles titanium x (47.87 grams titanium / 1 mole) = 22.6 grams

Hence,  the mass (in grams) of 0.473 mol of titanium is 22.6 grams.

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Answer:

5.6 × 10-5 m^3

Explanation:

Hope this helps

Answer:

all the below are ACIDS

Explanation:

1.HCOO- Formate

  HCOO- is a conjugate base.

2.HNO3- Nitric Acid

  Acid

3.CH3COOCH3: Methyl acetate

   Acid

4. HCOOH: Formic Acid

   Acid

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Answer:

mg

Explanation:

Answer:

the number of electrons is 13 and neutrons is 14

Answer:

B. what happens when iron rusts in the presence of water

Explanation:

Chemistry is a branch of science involving the composition and changes of matter. In other words, a chemist, who is a trained specialist in the science of chemistry, seeks to answer questions related to properties of matter.

In this question, a chemist is most likely to study "what happens when iron rusts in the presence of water" because it involves a change in the chemical properties of a substance (iron) i.e. a chemical change. However, what happens when ice melts to liquid water is a physical change.

mendeleev arranged the elements in order of increasing relative atomic mass. When he did this he noted that the chemical properties of the elements and their compounds showed a periodic trend

Answer:

Left to right

Elements are arranged by increasing atomic mass

Answer:

We do something called hypothesis

Answer:

1. Make an observation.

2. Ask a question.

3. Propose a hypothesis.

4. Make predictions.

5. Test the predictions.

6. Iterate.

and if it can't be trsted the you did something wrong

Explanation:

The scientific method

At the core of biology and other sciences lies a problem-solving approach called the scientific method. The scientific method has five basic steps, plus one feedback step:

Make an observation.

Ask a question.

Form a hypothesis, or testable explanation.

Make a prediction based on the hypothesis.

Test the prediction.

Iterate: use the results to make new hypotheses or predictions.

The scientific method is used in all sciences—including chemistry, physics, geology, and psychology. The scientists in these fields ask different questions and perform different tests. However, they use the same core approach to find answers that are logical and supported by evidence.

Scientific method example: Failure to toast

Let's build some intuition for the scientific method by applying its steps to a practical problem from everyday life.

Answer:

pH = 2.10

Explanation:

We name an acid as diprotic because it can release two protons:

H₂A  +  H₂O  ⇄  H₃O⁺   + HA⁻     Ka₁

HA⁻  +  H₂O  ⇄  H₃O⁺   + A⁻²      Ka₂

We propose the mass balance:

Analytical concentration = [H₂A] +  [HA⁻]  + [A⁻²]

As Ka₂ is so small, we avoid the [A⁻²] so:

0.18 M = [H₂A] +  [HA⁻]

But we can not avoid the HA⁻, because the Ka₁. Ka₁'s expression is:

Ka₁ = [H₃O⁺] . [HA⁻] / [H₂A]

We propose the charge balance:

[H₃O⁺] = [HA⁻] + [A⁻²] + [OH⁻]

As we did not consider the A⁻², we can miss the term and if

Kw = H⁺ . OH⁻

We replace Kw/H⁺ = OH⁻. So the new equation is:

[H₃O⁺] = [HA⁻] + Kw / [H₃O⁺]

The acid is so concentrated, so we can avoid the term with the Kw, so:

[H₃O⁺] = [HA⁻]

In the mass balance we would have:

0.18 M = [H₂A]

We replace at Ka₁

Ka₁ = [H₃O⁺] . [HA⁻] / [H₂A]

Ka1 . 0.18 / [H₃O⁺] = [HA⁻]

We replace at the charge balance:

[H₃O⁺] = Ka1 . 0.18 / [H₃O⁺]

[H₃O⁺]² = 3.4×10⁻⁴  . 0.18

[H₃O⁺] = √(3.4×10⁻⁴  . 0.18)

[H₃O⁺] = 7.82×10⁻³

- log [H₃O⁺] = pH → - log 7.82×10⁻³

pH = 2.10

Following are the calculation to the pH:

For First ionization:

[tex][H^+] = (K_{a1} \times C)^{\frac{1}{2}}[/tex]

where

C = initial concentration of acid [tex]= 0.18\ M[/tex]

[tex][H^{+}] = (3.4 \times 10^{-4} \times 0.18 \ M)^{\frac{1}{2}}\\[/tex]

[tex][H^{+}] = 0.007\ M[/tex]

For Second ionization:

[tex][H^{+}] = K_{a2} \\\\[/tex]

[tex][ H^{+} ] = 6.7 \times 10^{-9}\ M \\[/tex]

[tex]Total [H^{+}] = 0.007\ M + 6.7 \times 10^{-9}\ M\\\\Total [H^{+}] = 0.007 \ M[/tex]

[tex]pH = -\log[H^+] \\\\pH = -\log(0.007 \ M)\\\\pH = 2.15[/tex]

Therefore, the pH is "2.15".

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Answer: .B. 13C NMR spectra display peaks for only carbons that bear hydrogen atoms.

Explanation:

The statements that are true about 13C NMR are:

A. In 13C proton-decoupled NMR spectra, all peaks are singlets.

C 13C NMR chemical shifts occur over a greater range than 1H NMR chemical shifts.

D. 13C NMR easily differentiates between the different hybridized carbons (sp3, sp2, and sp hybridized carbons).organic-chemistry

Therefore, the option that isn't true is option B. "13C NMR spectra display peaks for only carbons that bear hydrogen atoms". This is false because 13C NMR will show every peak in the spectrum and it doesn't matter if it's only carbons that bear hydrogen atoms as everything will be shown.

Answer:

(i). The elements that are likely to form a cation

(C). calcium, (D). barium, (E). cesium, (F). rubidium, (G).  lead and (H). scandium

(ii). The elements those that will always form ionic compounds in a 1:2 ratio with the halogens

(B).  lead, (G) barium and (I). calcium

Explanation:

Given that,

The following list of elements,

A. oxygen B. chlorine C. calcium D. barium E. cesium F. rubidium G. lead H. scandium I. phosphorous

We know that,

Cation is defined as, an element which is able to donate electron easily and obtained positive ion.

All metal elements able to form cations.

We need to find the elements that are likely to form a cation

Using given list

(C). calcium

(D). barium

(E). cesium    

(F). rubidium    

(G).  lead

(H). scandium

(II). The following list of elements,

A. phosphorous B. lead C. chlorine D. cesium E. rubidium F. scandium G. barium H. oxygen I. calcium  

We know that,

All given metal ions can form ionic compound with halogens as 1:2 ratio because all given metals can form +2 charge.

We need to calculate the elements those that will always form ionic compounds in a 1:2 ratio with the halogens

Using given list.

(B).  lead

(G) barium

(I). calcium

Hence, (i). The elements that are likely to form a cation

(C). calcium, (D). barium, (E). cesium, (F). rubidium, (G).  lead and (H). scandium

(ii). The elements those that will always form ionic compounds in a 1:2 ratio with the halogens

(B).  lead, (G) barium and (I). calcium

Answer:

To get a final result of experiments, an experiment is repeated several times and the result is noted every time to make sure the results are consistent.

Here the "consistent" meaning is either "same" or "nearby". Consistent results are required in experiments that show constant relation of an experiment to the same principles and the result is not different when performed the same experiment several times.

When performing the same experiment several times, the end result of each experiment should consistent means adhered to the same principle for a successful experiment.

Answer:

pH = 1.683

Explanation:

plz mark as brainliest if it helps

B and C are ur answers

Answer:

The coordination number of ZrO₂ = 6

Explanation:

A crystal structure is determined by the ratio of ionic radii of the positive and negative ions present in the crystal.

The  ratio of the radii of the positive(cations) and negative(anions) is called the limiting radius ratio and it gives the coordination number of the crystal.

Limiting radius ratio = radius of cation/radius of anion

For ZrO₂:

radius of Zr ion (Zr⁴⁺) = 0.079 nm; radius of O ion (O²⁻) = 0.140 nm

Limiting radius ratio = 0.079 nm/0.140 nm = 0.564

From tables, when the limiting radius ratio value is between 0.414 - 0.732, the coordination number is six and the shape of the crystal is octahedral.

Therefore, the coordination number of ZrO₂ = 6

Answer:

because if the hotness should more it will give it increase the temperature of earn water but it is not so because you have taken out hands from your and cold water So it is reliable

Answer:

Explanation:

Polyatomic ions are ions (usually anions) that are made up of more than one atom. In order to determine the charge of anions, one can first identify the charge of the metal (which forms the cation) in a compound (which is usually easy to know) before predicting the charge of the anion. The charges are usually exchanged to form denominator of the other reacting atom/molecule, but if divisible, they are divided first before the exchange.

(a) The polyatomic ion in KNO₂ is NO₂ with the ionic equation below showing it's charge

KNO₂  ⇒ K⁺ + NO₂⁻

From the above, we can deduce that the charge of NO₂ is "1-"

(b) The polyatomic ion in CaSO₄ is SO₄ with the ionic equation below showing it's charge

CaSO₄ ⇒ Ca²⁺ + SO₄²⁻

The charge of SO₄ from the above equation is "2-"

(c) The polyatomic ion in Mg(NO₃)₂ is NO₃ with the ionic equation below showing it's charge

Mg(NO₃)₂   ⇒ Mg²⁺  +  NO₃⁻

From the above equation, it can be deduced that the charge of NO₃ is "1-"

Answer:

Explanation:

1 ) Let the lattice energy per mole be x

2 K + Cl₂ =  2KCl

Applying Born- Haber cycle

2 x 89 + 2 x 419 + 243 - 2 x 349  + Δx = - 2 x 436.5

178 + 838+ 243 - 698 + Δx = - 873

Δx = 1434 kJ

Lattice energy per mole = 1434 / 2 = 717 kJ / mol

2 )

2Ca + O₂ = 2 CaO

Heat of formation of CaO = - 635 kJ

Let lattice energy be x / mol

Bond energy of oxygen = 498 kJ / mol

178 x 2 + 2 ( 590 + 1145 ) + 498 + 2 ( 744 - 141 ) + x = - 2 x 635

356 + 3470 + 1206 + 498 + 2 x = - 1270

5530 + 2 x = - 1270

x = - 3400  kJ

The lattice energy for each specie can be calculated form the Born - Haber cycle and Hess law.

a) Given that;

Heat of formation (ΔH∘f) = -436.5 kJ/mol

Ionization energy (IE) = 419 kJ/mol

Heat of sublimation(ΔHsub) = 89.0 kJ/mol

Bond energy (BE) = 243 kJ/mol

Electron affinity (EA) =  -349 kJ/mol

Lattice energy (U) = ?

From Hess law;

ΔH∘f = ΔHsub + BE + IE + EA + U

U = ΔH∘f - [ΔHsub + BE + IE + EA]

U = ( -436.5 kJ/mol) -  [89.0 kJ/mol + 243 kJ/mol +  419 kJ/mol + ( -349 kJ/mol)]

U = -838.5  kJ/mol

b)

Heat of formation (ΔH∘f) =-635 kJ/mol

Ionization energy (IE) =IE1 + IE2 = 1735  kJ/mol

Heat of sublimation(ΔHsub) = 178kJ/mol

Bond energy (BE) = 498 kJ/mol

Electron affinity (EA) =  EA1 + EA2 = 603 kJ/mol

Lattice energy (U) = ?

From Hess law;

ΔH∘f = ΔHsub + BE + IE + EA + U

U = ΔH∘f - [ΔHsub + BE + IE + EA]

U = (-635 kJ/mol) - [ 178kJ/mol + 498 kJ/mol + 1735  kJ/mol + 603 kJ/mol]

U = -3649 kJ/mol

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Answer:

Fluorine

Fluorine is the element in question, as its atomic number is 9 . You would name this particular isotope using the mass number. It would be called fluorine-19.

Explanation:

Answer:

Fluorine

Fluorine is the element in question, as its atomic number is 9 . You would name this particular isotope using the mass number. It would be called fluorine-19.

Answer:

The necklace is fake.

The necklace is made up of copper.

Explanation:

The following data were obtained from the question:

Mass of the necklace = 21.3 g

Volume of water = 5 mL

Volume of water + Necklace = 7.4 mL

To identify the composition of the necklace, we shall determine the density of the necklace.

This can be obtained as follow:

We'll begin by calculating the volume of the necklace. This can be obtained as shown below:

Volume of water = 5 mL

Volume of water + Necklace = 7.4 mL

Volume of Necklace =.?

Volume of Necklace = (Volume of water + Necklace) – (Volume of water)

Volume of Necklace = 7.4 – 5

Volume of Necklace = 2.4 mL

NOTE:

1 mL = 1 cm³

Therefore,

Volume of Necklace = 2.4 mL = 2.4 cm³

Finally, we shall determine the density of the necklace as follow:

Mass of the Necklace = 21.3 g

Volume of Necklace = 2.4 cm³

Density of Necklace =?

Density = mass /volume

Density = 21.3 / 2.4

Density = 8.87 g/cm³

Therefore, the density of the necklace is 8.87 g/cm³.

From the question given above, we were told Jacy bought a gold necklace.

But comparing the density of necklace to the densities given above the necklace is obviously made of copper material.

Therefore, Jacy bought a fake gold necklace.

Answer:

C,  hydrogen.

Explanation:

Answer: Attractive forces between particels

Explanation:

Answer:

The temperature at which each bean is kept

Explanation:

Independent variable is what YOU CHANGE

The temperature at which each bean is kept is the independent variable.

INDEPENDENT VARIABLE:

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Answer:

it is a mixture

element are pure and compound are formed in a fixed ratio

Explanation:

Answer:

Theoretical yield = 3.75g

Explanation:

Percent yield is defined as one hundred times the ratio between actual yield and theoretical yield. The expression is:

Percent yield = Actual Yield / Theoretical Yield * 100

In the problem, your actual yield was 3-00g.

Percent yield is 80.0%.

Solving for theoretical yield:

80% = 3.00g / Theoretical yield * 100

Theoretical yield = 3.00g / 80.0% * 100

Answer:

Distance = 1500miles

time taken = 3 hours

speed of plane = distance/time taken = 1500/3= 500milesperhour

Explanation:

According to the distance formula , the speed of the plane is 500 miles per hour.

The speed of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit interval of time indicating that it is thus a scalar quantity.The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero. Speed is not the same as velocity.

Speed has the dimensions of distance divided by time. The SI unit of speed is the metre per second (m/s), but the most common unit of speed in everyday usage is the kilometre per hour (km/h) or in the US and the UK, miles per hour (mph).

Here, speed is calculated as distance /time= 1500/3= 500 miles per hour.

Thus, the speed of plane is 500 miles per hour.

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Answer:

Due to different atoms and different values of electronegativities.

Explanation:

NH3 and SO3 have different bond angles because both molecules have different type of atoms combine together. In NH3, nitrogen react with hydrogen while in SO3, sulfur react with oxygen atom. The bond angle of NH3 is 107 while the bond angle of SO3 is 120. This difference in bond angle is also due to different electronegativities of the bonded atoms. The electronegativity of oxygen is higher than hydrogen so repulsion of hydrogen is less and that's why its bond angle is also lower than oxygen.

Answer:

False

Explanation:

Science is not based on primarily on peoples opinions and views of the subject matter whereas science is based on empirical observations and research for its validity.

Science aims to find answers to human questions related to the natural world through their research observation and experiments. Scientists and researchers provide valid proof of human questions so that people can trust them.

Science can change people's opinions regarding the natural world with valid proof and observational theories but science is not based on people's opinion.

Hence, the given statement is "false".

Answer:

36690

Explanation: