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2 years ago

Describe it what is the scientefic method??

Chemistry

1 answer:

WINSTONCH [101]2 years ago

5 0

It is the principles and procedures for the systematic pursuit of knowledge involving the recognition and formulation of a problem, the collection of data through observation and experiment, and the formulation and testing of hypotheses

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A geologist studies layered rock to determine its age. Bacteria fossils from the Precambrian age are found in the rock’s upper l

kondor19780726 [428]

Answer:
The bottom layers of the rock could have formed before life occurred.

Explanation:
The bottom layers of the rock could have formed before life occurred because there is no fossil is present. If there is life at that time so the fossils are present at the bottom layer so the absence indicates that is no life present at that time. The bottom layer is older than the upper layer so that's why fossils of bacteria are found in the upper layer of the rock.

Answer:
C. Because bacterial fossils are found only in the upper layers, scientists can conclude that these bacteria evolved towards the end of Precambrian time.

There’s two different types of answers for this question so I just put both of them. Hope it helps : )

4 0

2 years ago

UGRENT! Please help showing all work

agasfer [191]

Answer:

a. The limiting reactant is Ca(OH)₂

b. The theoretical yield of CaCl₂ is approximately 621.488 grams

c. The percentage yield of CaCl₂ is approximately 47.06%

Explanation:

a. The given chemical reaction is presented as follows;

Ca(OH)₂ + 2HCl → CaCl₂ + 2H₂O

Therefore;

One mole of Ca(OH)₂ reacts with two moles of HCl to produce one mole of CaCl₂ and two moles of water H₂O

The mass of HCl in an experiment, m₁ = 229.70 g

The mass of Ca(OH)₂ in an experiment, m₂ = 207.48 g

The molar mass of HCl, MM₁ = 36.458 g/mol

The molar mass of Ca(OH)₂, MM₂ =74.093 g/mol

The number of moles of HCl, present, n₁ = m₁/MM₁

∴ n₁ = m₁/MM₁ = 229.70 g/(36.458 g/mol) ≈ 6.3 moles

The number of moles of Ca(OH)₂, present, n₂ = m₂/MM₂

∴ n₂ = m₂/MM₂ = 207.48 g/(74.093 g/mol) ≈ 2.8 moles

The number of moles of Ca(OH)₂, present, n₂ = 2.8 moles

According the chemical reaction equation the number of moles of HCl the 2.8 moles of Ca(OH)₂ will react with, = 2.8 × 2 moles = 5.6 moles of HCl

Therefore, there is an excess HCl in the reaction and Ca(OH)₂ is the limiting reactant

b. According the chemical reaction equation the number of moles of CaCl₂ produced in he reaction by the 2.8 moles of Ca(OH)₂ = 2.8 × 2 moles = 5.6 moles of CaCl₂

The molar mass of CaCl₂ = 110.98 g/mol

The mass of the 5.6 moles of CaCl₂ = 5.6 moles × 110.98 g/mol ≈ 621.488 grams

The theoretical yield of CaCl₂ ≈ 621.488 grams

c. Given that the actual mass of CaCl₂ produced = 292.5 grams, we have;

The percentage yield of CaCl₂ = The actual yield/(The theoretical yield) × 100

∴ The percentage yield of CaCl₂ = (292.5 g)/(621.488 g) × 100 ≈ 47.0644646397%

The percentage yield of CaCl₂ ≈ 47.06%.

8 0

3 years ago

Two aircraft rivets, one iron and the other copper, are placed in a calorimeter that has an initial temperature of 20.°C. The da

Igoryamba

The heat will flow from Cu to Fe because Cu has higher temperature and has lower peak value .

Given ,

two aircraft rivets , one iron and the other copper , are placed in a calorimeter .

the initial temp of the calorimeter is 20 degC .

mass of iron = 30 g

initial temp of iron = 0 degC

Mass of copper = 20 g

initial temp of copper = 100 degC

Here copper has higher temp ,thus heat flow from Cu to Fe .

Heat flow is the movement of heat from higher temperature to lower temperature .

<h3>What is calorimeter ?</h3>

It is an object used for measuring the heat flow , heat capacity of a chemical reaction as well as the physical changes .

Learn more about calorimeter here :

brainly.com/question/1407669

#SPJ4

8 0

1 year ago

Ultraviolet radiation and radiation of shorter wavelengths can damage biological molecules because they carry enough energy to b

Lelechka [254]

Answer:

343.98 nm is the longest wavelength of radiation with enough energy to break carbon–carbon bonds.

Explanation:

A typical carbon–carbon bond requires 348 kJ/mol=348000 J/mol

Energy required to breakl sigle C-C bond:E

$E=\frac{348000 J/mol}{6.022\times 10^{23} mol^{-1}}=5.7788\times 10^{-19} J$

$E=\frac{h\times c}{\lambda}$

where,

E = energy of photon

h = Planck's constant = $6.626\times 10^{-34}Js$

c = speed of light = $3\times 10^8m/s$

$\lambda$ = wavelength of the radiation

Now put all the given values in the above formula, we get the energy of the photons.

$\lambda =\frac{(6.63\times 10^{-34}Js)\times (3\times 10^8m/s)}{5.7788\times 10^{-19} J}$

$\lambda =3.4398\\times 10^{-7}m=343.98 nm$

$1 m = 10^{9} nm$

343.98 nm is the longest wavelength of radiation with enough energy to break carbon–carbon bonds.

4 0

3 years ago

Which isotope is used to treat cancer?<br> (1) C-14 (3) Co-60<br> (2) U-238 (4) Pb-206

lions [1.4K]

I believe doctors use (3) Co-60 to treat ILWs. Uranium and Carbon are not used, and a different isotope of lead is used to be attached to monoclonal antibodies.

8 0

3 years ago