How to solve for enthalpy for changes​

Answer:

B.  Na

Explanation:

To identify an atom, you simply need to look at the number of protons.  This atom has 11 protons.  On the periodic table, you can see that the element with 11 protons is sodium (Na).

Answer:

Explanation:

There are 3 types of plastids :-

1) Chloroplasts:- The green plastids which contain chlorophyll pigments for photosynthesis.

2) Chromoplasts:-The coloured plastids for pigment synthesis and storage.

3) Leucoplasts:- The colourless plastids for monoterpene synthesis found in non- photosynthetic parts of the plants.

They are of three types:-  

a) Amyloplasts- stores starch.

b) Proteinoplasts-  stores proteins.

c) Elaioplasts- stores fats and oils.

Answer: crushing a can, boiling water, breaking a glass

Explanation:

the  Answer is C

Both the atomic mass and the atomic number increase from left to right.

Answer: is C

Explanation:

Both the atomic mass and the atomic number increase from left to right

Answer:

(simple differences)Biodegradable substances are those that degrades or break down naturally...

Non-biodegradable substances are those that do not degrades easily...

Answer:

Biodegradable substances are those that degrades or break down naturally

Non-biodegradable substances are those that do not degrades easily

Answer:

formed at earths surface

Explanation:

so easy

Answer: because the very polar water molecules attract both the positively charged sodium ions and the negatively charged chloride ions.

Answer:

Explanation:a

Scientific predictions are best described as consistent data that are presented in the form of if and then. It is a solution to the problem that may be identified. Thus, option a is correct.

Scientific prediction is a statement that describes the events of the future that are not always correct or incorrect. In scientific research, the experiment is conducted based on the hypothesis to draw conclusions and results that are expected.

The expected results are said to be scientific predictions when they are represented in the form of "if and then" before the analysis of the experimental method and its result are done. It is an account of the events that may possibly take place under specific conditions.

Therefore, option A. scientific prediction is an expected problem.

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Your height should be measured in meters. Centimeters is much too small of a unit to measure the several feet most people are.

Answer:

scientists benefit the society because they prove many theories, plus they are always finding new solutions to new things

Explanation:

Answer:

The scientist uses specialized training to help solve problems

faced by society.

Explanation:

A P E X

Answer: Meteorhpayne

Explanation: Correct me if im wrong :(

Answer:

Explanation:

A mixture of a weak acid and its conjugate base (or a mixture of a weak base and its conjugate acid) is called a buffer solution, or a buffer. Buffer solutions resist a change in pH when small amounts of a strong acid or a strong base are added (Figure 1). A solution of acetic acid and sodium acetate (CH3COOH + CH3COONa) is an example of a buffer that consists of a weak acid and its salt. An example of a buffer that consists of a weak base and its salt is a solution of ammonia and ammonium chloride (NH3(aq) + NH4Cl(aq)).

The pH of the resulting buffer solution is 6.60.

pH of acidic  buffer solution is calculated by Henderson equation which is,

    pH =pK[tex]_a[/tex] +log[salt]/log[acid]

As the buffer is diluted the concentration is reduced to half, that is

[acid]=0.075 M

[salt]=0.02 M    pK[tex]_a[/tex]=4.74

substituting these values in Henderson's equation for acid buffers,

pH=4.74+log[0.075]/[0.02]

     =6.6071

Thus, the pH of resulting buffer solution is 6.6071.

Acid buffers  consist of a solution  of weak acid  and its salt.A commonly used acid buffer is  prepared by mixing  acetic acid and sodium acetate.

Henderson equation is used to calculate pH of buffer solution and ratio of salt to acid to prepare acid solution. pK[tex]_a[/tex] for acid buffers is constant.

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Answer:

A.  Peroxide breaking down into water and oxygen

Explanation:

Generally when it comes to changes, there are physical and chemical changes. In physical changes, there are no new substances been formed, however in chemical change new substances are formed.

A.  Peroxide breaking down into water and oxygen

This is a chemical change.

B . Bubbles forming when a pot of water is heated

This is a physical change

C. A pair of jeans soaked in water drying after hanging outside

This is a physical change

D . A block of ice decreasing in size due to a change in temperature

This is a physical change.

Only option A is different from the rest,hence this is the answer.

Answer: The density of the rock is 2g/mL. Hope this helped! :)

Explanation:

V= 3.0mL                                                               D=M/V

M= 6.0g

D=6.0g/3.0mL

D= 2.0g/mL

Answer:

3). Chemical potential energy

1). lower in charcoal than in coal.

Explanation:

Chemical potential energy is defined as the energy that can be absorbed or stored in a substance's chemical bonds. It can be released when there is a change in the number of particles of the substance.

As per the question, coal releases more heat than charcoal because 'the chemical potential energy of charcoal is lower than the coal' and hence, the latter would release more heat on burning i.e. the energy that was absorbed in the chemical bonds of the substance. Hence, option 3 and 1 are the correct answers.

Answer:

5

Explanation:

you have two zeros that are sandwiched in between and one following a signifincant figure after the decimal.

Answer: An air mass that originates over land in Central America is most likely warm & dry.

Answer:

he oxygen ion you have with 8 protons attracting 10 electrons is larger, ... As a result, the 3Al3+ ion will be smaller than the Si element, which has ... O<Al3+<Si<Al<O2-<Ag<Rb<Cs ... It is fairly easy to arrange the atoms according to atomic size. ... I would put it between Al and Ag .

Explanation:

A wind-up toy that is not wound up will have Potential Energy Hence, The correct option is Option (B)

Potential energy is that the energy control by associate object due to its position relative to alternative objects, stresses among itself, its charge, or alternative factors.

The total energy of a mechanical toy is given as follows ;

Total Mechanical Energy = Kinetic Energy + Potential Energy

During the winding up of the coil, the total energy becomes the kinetic energy

The total energy at the point of winding up of the coil = The kinetic energy supplied to the toy by winding the coil

From the first law of thermodynamics, energy can not be created nor destroyed however may be modified from one type to a different

Due to the coil being prevented from unwinding, the kinetic energy stored as Potential energy of the toy

When the toy is operated it then unwinds the coil bringing about motion and converting back the potential energy to kinetic energy by itself as if it was alive.

Therefore, A wind-up toy that is not wound up will have Potential Energy Hence, The correct option is Option (B)

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Answer:

Im pretty sure the answers b

Explanation:

Because if its talking about overall tempature the it means ihas tension with high surface.

Answer:

The total measurements of the oil is 3.45mL

Explanation:

Given

1.5 mL, 0.75 mL, and 1.2 mL.

Required

Determine the total

To get the total, we simply add the given volumes together.

[tex]Total = 1.5 mL+ 0.75 mL + 1.2 mL[/tex]

[tex]Total = 3.45mL[/tex]

Hence;

The total measurements of the oil is 3.45mL

Answer:

match emit 350 J light energy.

Explanation:

By law of conservation of energy,  total energy before and after reaction for an isolated system remains constant.

Total energy for unlit match = 1000 j

When it burns type of energy released

thermal energy = 400 j

light energy --> it value is unknown which we have to find

also remaining match has 250 joule of chemical energy

applying   law of conservation of energy

energy before match was unlit = energy after match was lit

1000 j = thermal energy + light energy + chemical energy of remaining match

1000 J = 400 J  + light energy + 250 J

light energy = 1000 J - 400J - 250J

light energy = 350 J

Thus, match emit 350 J light energy.

Answer: D. All of the above

Answer:

B. Alpha Particles

Explanation:

P: Have a Nice Day!

Answer:

A:DNA is a double helix, and RNA is a single strand.

C:DNA is involved only in transcription, and RNA is involved in both transcription and translation.

E:DNA does not have uracil as a nitrogen base, but RNA does have uracil as a nitrogen base.

Explanation:

I did the test an Edge.

Answer:

8.3334%

Explanation:

You have two masses. To find the percent of sodium chloride in water by mass, you divide the mass of NaCl by water. First, make both units the same. Easiest is to convert kg into g. 1.5kg = 1500g

125g NaCl/1500g H2O = 0.0833333333 ==> 8.3334%

Answer:

adding or removing protons

Explanation:

Elements are defined by the number of protons they have. If you add or subtract protons then that changes and makes a new element.

Answer:

by changing the number of protons in the nucleus

Complete question :

A jeweler has five rings, each weighing 18 g, made of an alloy of 10% silver and 90% gold. She decides to melt down the rings and add enough silver to reduce the gold content to 75%. How much silver should she add?

Answer:

Kindly check explanation

Explanation:

Given the following :

Weight of each alloy = 18g

Initial % of Silver = 10% = 0.1

Initial % of Gold = 90% = 0.9

New % of gold = 75% = 0.75

Hence, new % of silver will be (1 - 0.75) = 0.25

Let the amount of silver to be added = s

Hence,

Initial gold content = final gold content + added silver

18 * 0.9 = 0.75(18 + s)

16.2 = 13.5 + 0.75s

16. 2 = 13.5 + 0.75s

16.2 - 13.5 = 0.75s

2.7 = 0.75s

s = 2.7 / 0.75

s = 3.6

S = 3.6

Hence the amount of silver needed per ring in other to reduce the gold content = 3.6g

Total for the 5 rings = (3.6 * 5) = 18g

Dimensional analysis is the unitary method that is used to determine the values by multiplication. The cost of the ice cream sandwiches for the barbecue is 367.5 $.

Dimensional analysis has been defined in maths, physics, and chemistry to solve the problem by multiplying the given numbers to determine the values of the other data. It uses the base quantities to estimate the derived values.

Given,

Number of people at barbecue = 175

Cost of ice cream sandwiches = $1.68 per dozen

The average number of sandwiches per person = 1.25

The cost to buy ice cream sandwiches for the barbecue is estimated by the dimensional analysis as:

12 ice cream sandwiches = $1.68

1.25 ice cream sandwiches = $2.1

If it costs $2.1 for each person then 175 people costs:

$2.1 × 175 = $367.5

Therefore, it will cost 367.5 $ for the barbecue.

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