Answer: The digestive system breaks down food into nutrients that are transported by the circulatory system.
Explanation:
An organ system includes the organs which are linked to one another to perform a physiological function in the body of the organism. The digestion is a complex process in which the food is being broken down into sub-components so that it can be assimilated in the body. The digestive system involves the multiple organs like mouth, esophagus, stomach, intestines and others. The food being digested is absorbed in the bloodstream, which circulate in the vital organs of the body like lungs, heart, vascular system hence, the blood becomes the part of the circulatory system.
Thus it can be said that the argument of children that the two systems are related is justified by the digestive and circulatory system of the body.
Calculate the pH of a 0.020 M H2CO3 solution. At 25 °C, Ka1 = 4.3 × 10-7. H2CO3(aq) + H2O(l) ↔ H3O+(aq) + HCO3-(aq)
Answer:
Explanation:
H₂CO₃(aq) + H₂O(l) ↔ H₃O⁺(aq) + HCO₃⁻(aq)
Let d be the degree of dissociation
.02( 1-d ) .02d .02d
Dissociation constant Ka₁ is given
4.3 x 10⁻⁷ = .02d x .02d / .02( 1-d )
= .004 d² / .02 ( neglecting d in denominator )
= .02 d²
d² = 215 x 10⁻⁷
d = 4.636 x 10⁻³
= .004636
concentration of H₃O⁺
= d x .02
= .004636 x .02
= 9.272 x 10⁻⁵
pH = - log [ H₃O⁺ ]
= - log ( 9.272 x 10⁻⁵ )
5 - log 9.272
= 5 - .967
= 4.033 .
3 Pieces of Key Information elements, compounds, mixtures also state a real world example of elements, compounds, mixtures and lastly why is elements, compounds, mixtures are important
Answer:
Element and compounds are the pure substances but mixture is not a pure substance.
Explanation:
Element and compounds are the pure substances in which element comprise of only one atom while compound is formed by the chemical combination of more than one element in a fixed ratio by mass while mixture is also made up of more that one substances but they are combine physically not chemically. Elements, compounds, mixtures are very important because all the materials we used in our daily life are formed from elements, compounds and mixtures.
If 200.4g of water is mixed with 101.42g of salt the mass of the final solution would be reported as
Answer:
301.8 g
Explanation:
We prepare a solution with 200.4 g of water (solvent) and 101.42 g of salt (solute). The mass of the solution is equal to the sum of the mass of the solvent and the mass of the solute.
m(solution) = m(solute) + m(solvent)
m(solution) = 200.4 g + 101.42 g
m(solution) = 301.8 g (we round-off to one decimal according to the significant figures rules)
Fill in the blank: If an atom is in column V (or 15), it will most likely ____________ to fulfill the octet rule.
Gain 3 electrons
Lose 5 electrons
Gain 5 electrons
Lose 5 protons
Gain 3 protons
Answer:
If an atom is in column V (or 15), it will most likely gain 3 electrons to fulfill the octet rule.
Explanation:
The octet rule defines the property that atoms have to complete their last energy level with eight electrons to achieve stability through an ionic, covalent or metallic bond.
The pair of electrons that are transferred or gained belong to the last shell of the atom. If an atom is in column V (or 15), it means that it has 5 electrons in its last shell. So an atom in this group is more likely to gain 3 electrons to achieve stability than to lose the 5 electrons it has.
If an atom is in column V (or 15), it will most likely gain 3 electrons to fulfill the octet rule.
A. Gain 3 electrons
What does Octet rule say?The octet rule defines the property that atoms have to complete their last energy level with eight electrons to achieve stability through an ionic, covalent or metallic bond.
The pair of electrons that are transferred or gained belong to the last shell of the atom. If an atom is in column V (or 15), it means that it has 5 electrons in its last shell. So an atom in this group is more likely to gain 3 electrons to achieve stability than to lose the 5 electrons it has.
Thus, correct option is A.
Find more information about Octet rule here:
brainly.com/question/865531
During which stage of the water cycle could water enter the atmosphere as a gas? A. transpiration B. precipitation C. accumulation D. condensation
Answer: Transpiration---A
Explanation: Transpiration is the process in the water cycle whereby plant loose(excess) water by evaporation through the stomata of their leaves since not all water absorbed by the root is actually used for growth in plants.In order to allow the intake of carbon-dioxide, water must exit the leaves through transpiration which then provides the plant with cooling, rigidity and maintaining the overall water balance of the plant.
What is the reactant(s) in the chemical equation below?
2Al(s) + 2NaOH(aq) + 2H2O()
2NaAlO2(aq) + 3H2(9)
A. 2Al(s) + 2NaOH(aq) + 2H200)
B. 2NaAlo2(aq) + 3H2(g)
C. 2Al(s)
D. 3H2(g)
Answer:
A
Explanation:
They are all found in the reactants side
In this problem, you will use Lenz's law to explore what happens when an electromagnet is activated a short distance from a wire loop.
You will need to use the right-hand rule to find the direction of the induced current. When the switch is open, which of the following statements about the magnetic flux through the wire loop is true? Assume that the direction of the vector area of the wire loop is to the right.
A) There is no magnetic flux through the wire loop.
B) There is a positive flux through the wire loop.
C) There is a negative flux through the wire loop.
Answer:
The correct answer is Option A (There is no magnetic flux through the wire loop.)
Explanation:
Magnetic flux measures the entire magnetic field that passes through the wire loop.
The right hand rule can be demonstrated on how magnetic flux is generated through the moving current in the wire loop. The magnetic flux through the wire loop will decrease as it moves upward through the magnetic field region.
If the direction of the vector area of the wire loop is to the right, and the switch is closed, it will push the magnetic flux to the right which will now be increased due to an equal increase in the current in the wire loop. But, when the switch is open, this will halt the movement of current through the wire loop thus affecting the generation of magnetic field. This would make the magnetic flux to be zero.
The statement related to the magnetic flux is option A i.e. no magnetic flux is there.
What is magnetic flux?It determined the overall magnetic field that should be passed via the looping of the wire. here the right-hand rule represent how the magnetic flux should be created via the movement of the current.
Also, it should be decreased in the case when it should be moved upward. Also, in the case when the direction of the vector area should be right so the switch should be closed.
Therefore, the option A is correct.
Learn more about magnetic here: https://brainly.com/question/18704022
What must happen for an ionic bond to be created between two elements?
Answer:
they must be heated
Explanation:
Smooth muscle myosin is a motor protein that plays a crucial role in the contraction of smooth muscle. If this protein has a molar mass of 480,000 grams/mol, what is the mass, in grams, of 27 moles of smooth muscle myosin
Answer: Thus the mass, in grams, of 27 moles of smooth muscle myosin is 12960000 grams
Explanation:
According to avogadro's law, 1 mole of every substance weighs equal to the molecular mass, occupies 22.4 L at STP contains avogadro's number [tex](6.023\times 10^{23})[/tex] of particles.
Molecular mass of protein = 480,000 g/mol
Thus 1 mole of protein weighs = 480,000 g
So 27 moles of protein weighs = [tex]\frac{480,000}{1}\times 27=12960000g[/tex]
Thus the mass, in grams, of 27 moles of smooth muscle myosin is 12960000 grams
To determine the concentration of a sample of calcium hydroxide, 1.45M HCl is added drop-wise using a burst. Write the balanced net ionic equation for the acid-base reaction.
Answer:
H^+(aq) + OH^-(aq) —> H2O(l)
Explanation:
We'll begin by writing the balanced equation for the reaction.
2HCl(aq) + Ca(OH)2(aq) —> CaCl2(aq) + 2H2O(l)
Ca(OH)2 is a strong base and will dissociates as follow:
Ca(OH)2(aq) —> Ca^2+(aq) + 2OH^-(aq)
HCl is a strong acid and will dissociates as follow:
HCl(aq) —> H^+(aq) + Cl^-(aq)
Thus, In solution a double displacement reaction occurs as shown below:
2H^+(aq) + 2Cl^-(aq) + Ca^2+(aq) + 2OH^-(aq) —> Ca^2+(aq) + 2Cl^-(aq) + 2H2O(l)
To get the net ionic equation, cancel out Ca^2+ and 2Cl^-
2H^+(aq) + 2OH^-(aq) —> 2H2O(l)
H^+(aq) + OH^-(aq) —> H2O(l)
Problem PageQuestion Liquid hexane CH3CH24CH3 will react with gaseous oxygen O2 to produce gaseous carbon dioxide CO2 and gaseous water H2O. Suppose 60. g of hexane is mixed with 74.5 g of oxygen. Calculate the maximum mass of water that could be produced by the chemical reaction. Round your answer to 3 significant digits.
Answer:
43.45g of water would be produced from the reaction.
Explanation:
Liquid became reacts with oxygen to produce carbon dioxide and water.
This type of reaction is known as combustion reaction between alkanes.
Equation of reaction.
Assuming the reaction occurs in an unlimited supply of oxygen,
2C₆H₁₄ + 19O₂ → 12CO₂ + 14H₂O
From the above equation of reaction,
2 moles of C₆H₁₄ reacts with 19 moles of O₂ to produce 14 moles of H₂O.
To find the theoretical mass,
Number of moles = mass / molar mass
Molar mass of C₆H₁₄ = 86g/mol
Molar mass of O₂ = 16g/mol × 2 = 32g/mol
Molar mass of H₂O = 18g/mol
Mass of H₂O = number of moles × molar mass
Mass of H₂O = 14 × 18 = 252g
Mass of C₆H₁₄ = number of moles × molar mass
Mass of C₆H₁₄ = 2 × 86 = 172g
Mass of O₂ = number of moles × molar mass
Mass of O₂ = 19 × 32 = 608g
From the equation of reaction,
172g of C₆H₁₄ reacts with 608g of O₂ to produce 252g of H₂O
(172 + 608)g of reactants produce 252g of H₂O
780g of reactants produce 252g of H₂O
(60 + 75.5)g of reactants will produce a x g of H₂O
780g of reactants = 252g of H₂O
134.5g of reactants = x g of H₂O
X = (134.5 × 252) / 780
X = 43.45g of H₂O
Therefore, 43.45g of H₂O would be produced from 60g of hexane and 74.5g of oxygen
Answer:
[tex]m_{H_2O}=30.9gH_2O[/tex]
Explanation:
Hello,
In this case, the combustion of hexane is given by:
[tex]C_6H_{14}+\frac{19}{2} O_2\rightarrow 6CO_2+7H_2O[/tex]
The next step is to compute the reacting moles of hexane:
[tex]n_{C_6H_{14}}=60gC_6H_{14}*\frac{1molC_6H_{14}}{86gC_6H_{14}} =0.698molC_6H_{14}[/tex]
Then, the moles of hexane consumed by 74.5 g of oxygen using the molar ratio in the chemical reaction (1:19/2):
[tex]n_{C_6H_{14}}=74.5gO_2*\frac{1molO_2}{32gO_2} *\frac{1molC_6H_{14}}{19/2molO_2} =0.245molC_6H_{14}[/tex]
Therefore, as less moles of hexane are consumed by oxygen, it is in excess, so we compute the mass of water produced by the consumed 0.245 moles of hexane:
[tex]m_{H_2O}=0.245molC_6H_{14}*\frac{7molH_2O}{1molC_6H_{14}}*\frac{18gH_2O}{1molH_2O} \\\\m_{H_2O}=30.9gH_2O[/tex]
Best regards.
Gravity on Earth is 9.8 m/s2, and gravity on the Moon is 1.6 m/s2.
so if the mass of an object on earth is 40 kilograms what is the mass on the moon.
and how much does it way
Answer:
Mass is the same but it weights 64 Newtons
Explanation:
First of Mass is the same in any sort of gravity. Now let's calculate weight
W = MG
where W = Weight
M = Mass
G = Gravity
W = (40kg)(1.6)
W = 64
Sorry for the spelling mistakes, hope this helps
Answer:6.61kilo
Explanation: fdfv
g Reduction involves the A) loss of neutrons, gain of electrons, and an increase in oxidation state. B) loss of neutrons. C) increase in oxidation state. D) gain of electrons and an increase in oxidation state. E) gain of electrons.
Answer:
E. Gain of electrons
Explanation:
A reduction reaction is one part of the two concurrent reactions that take place in a redox (reduction-oxidation) reaction.
During reduction, an atom gains electrons from a donor atom, and it's oxidation number becomes smaller.
Option A is wrong because reduction does not increase oxidation state nor are neutrons involved
Option B is wrong because reduction is not a nuclear reaction (does not involve the nucleons)
Option C is wrong because reduction leads to reduction in oxidation state
Option D is wrong leads to a reduction in oxidation state when electrons are gained
Option E is correct because reduction involves gain of electrons
Coral reefs support more species per unit area than any other marine
environment on Earth. What role do coral reefs play in the health of the
biosphere?
A. Coral reefs tend to drain nearby wetlands of stagnant water.
B. Their productive organisms play a major role in nutrient recycling.
C. Their colorful organisms attract millions of tourists each year.
D. Coral reefs require very specific environmental conditions.
SUBMIT
Answer:
B. Their productive organisms play a major role in nutrient recycling.
Explanation:
Coral reefs contain photosynthetic algae that help coral reefs in processing nutrients and contribute in the nutrient cycle.
The process of photosynthesis in corals leads to carbon fixing in which corals transform, carbon dioxide, into organic carbon. carbon fixing property allows corals to become primary producers.
Dissolve organic matter produced by corals is consumed by several organisms such as crabs, worms, fish, and snails.
Hence, coral reefs maintain the flow of energy and nutrient cycle in the biosphere and the correct option is B.
The decay of a radioactive material is monitored using a Geiger counter. At the start, the count rate is 2000 decays/minute. Four hours later the decay rate is 500 counts/min. What is the half-life of the material?
Answer:
The half-life of the material is 2 years
Explanation:
Given;
initial count rate = 2000 decays/minute
final count rate = 500 counts/min
decay time = Four hours
To determine the half life of the material; we create a simple decay table that matches the decay time and count rates.
time (years) count rate
0 2000 decays/minute
2 1000 decays/minute
4 500 decays/minute
Half life is the time intervals = 2 years
Also using a formula;
[tex]N = \frac{N_o}{(t/2)^2} \\\\N_o-is \ the \ initial \ count\ rate\\\\N-is \ the \ final \ count\ rate\\\\t/_2 - is \ the\ half\ life \\\\N = \frac{N_o}{(t/2)^2} \\\\500 = \frac{2000}{(t/2)^2}\\\\(t/_2)^2 = \frac{2000}{500} \\\\(t/_2)^2 = 4\\\\t/_2 = \sqrt{4} \\\\t/_2 = 2 \ years[/tex]
Therefore, the half-life of the material is 2 years
Aspirin is usually packaged with
A. acetic anhydride
B. salicylic acid
C. buffering agents
Answer:
Aspirin is usually packaged with C. buffering agents.
Explanation:
Nitrogen forms more oxides than any other element. The percents by mass of in three different nitrogen oxides are (1) (II) and (III) 25.94 For each compound, determine (a) the simplest whole-number ratio of to and (b) the number of grams of oxygen per 1.00 of nitrogen.
Complete question;
Nitrogen forms more oxides than any other element. The percents by mass of N in three different nitrogen oxides are (|) 46.69%;(II) 36.85 %; (III) 25.94%. For each compound, determine (a) the simplest whole-number ratio of N to O, and (b) the number of grams of oxygen per 1.00 g of nitrogen.
Answer:
a. (i) The ratio is 1:1 , the formula = NO (ii)The ratio is 1 : 1.5 which is 2 : 3, the formula = N₂O₃ (iii) The ratio is 1 : 2.5 which is 2:5 , the formula = N₂O₅
b. (i)number of grams of oxygen = 53.31/46.69 = 1.14 g
(ii)number of grams of oxygen = 63.15/36.8 = 1.71 g
(iii)number of grams of oxygen = 74.06/25.94 = 2.855 g
Explanation:
a.
(i) The percentage by mass of the nitrogen in Nitrogen oxide (i) is 46.69% which is taken as 46.69 grams . Since the other element is oxygen the mass of oxygen will be 100 - 46.69 = 53.31 grams.
The relative atomic mass of Nitrogen and oxygen is 14 amu and 16 amu respectively.
Therefore, to know the whole number ratio of N and O we find the number of moles.
number of moles of N = 46.69/14 = 3.335
number of moles of O = 53.31/16 = 3.332
The ratio is 1:1 , the formula = NO
(ii)
number of moles of N = 36.85/14 = 2.632
number of moles of O = 63.15/16 = 3.947
The ratio is 1 : 1.5 which is 2 : 3, the formula = N₂O₃
(iii)
number of moles of N = 25.94/14 = 1.85
number of moles of O = 74.06/16 = 4.63
The ratio is 1 : 2.5 which is 2:5 , the formula = N₂O₅
b.
(i) 46.69 g of nitrogen = 53.31 g of oxygen
1 g of nitrogen = ? of Oxygen
number of grams of oxygen = 53.31/46.69 = 1.14 g
(ii)
Using similar method in b(i)
number of grams of oxygen = 63.15/36.8 = 1.71 g
(iii)
Using similar method in b(i)
number of grams of oxygen = 74.06/25.94 = 2.855 g
5. Rosalind Franklin was a key figure in the discovery of the structure of DNA, yet she
was not included in the Nobel Prize which was awarded to Watson and Crick. Carry out
some research to find out how she contributed to this work and use the space below
to write up your findings
Answer:
Explanation:
Search for "Rosalind Franklin: DNA's unsung hero - Cláudio L. Guerra" which basically summarizes what Rosalind did and how we was snubbed from receiving the noble prize even though she had vast and critical evidence to highlight the structure of DNA. You can look for more sources but I can tell you a quick recap:
Rosalind Franklin was born in an era where women scientists or workers were very uncommon and they were even discriminated and looked down upon. After her phD., she was working to find the structure of DNA and soon she was able to form an x-ray image of it. However, her lab colleague took the picture and showed it to other scientists (Watson and Crick) without the knowledge or permission of Rosalind. Here Rosalind was working on analyzing her data and on other part of world Watson and Crick were doing the same. Based on Watson and Crick's analysis, they came up with the correct structure of DNA and soon Rosalind got done as well. Both submitted their paper to journal, however, the journal placed Watson and Crick paper before Rosalind (making it look like Rosalind just confirmed what Watson and Crick proposed). This made it look like Watson and Crick were geniuses behind DNA structure whereas, in reality, it was Rosalind. She would have received Nobel Prize but she died of Cancer and Nobel prizes are not awarded to dead people.
Which of the following bases is the WEAKEST? The base is followed by its Kb value. Group of answer choices HOCH2CH2NH2, 3.2 × 10-5 (CH3CH2)3N, 5.2 × 10-4 NH3, 1.76 × 10-5 C5H5N, 1.7 × 10-9 Since these are all weak bases, they have the same strength.
Answer:
C₅H₅N being the weakest base
Explanation:
A weak base (B) is defined as a chemical compound that, in reaction with water, produce a small quantity of BH⁺
The general reaction is:
B + H₂O ⇄ BH⁺ + OH⁻ Where Kb is defined as:
Kb = [BH⁺] [OH⁻] / [B]
That means the smallest Kb is the weakest base because is producing the smallest quantity of BH⁺.
In the problem, the smallest Kb is C₅H₅N being the weakest base.
A maple tree could be studied in many fields of science. What aspects of a maple tree might be studied in chemistry?
Answer:
Chemical reactions, kinetics, organic chemistry
Explanation:
You might study the chemical reaction, learn about the differences between products and reactants, about delta H and exothermic and endothermic reactions. You may also study Kinetics by studying the rates of reactions with certain chemicals in a maple's enzymatic processes.
Another thing that you might learn about is organic chemistry. The glucose molecules, carbohydrates, lipids, nucleic acids, all have a structure based on the Carbon atom. You can learn about the specific structures of some chemicals that are involved in photosynthesis and simple hydrocarbons that are involved in photosynthetic/bio-synthetic pathways.
There's probably a lot more - but these are the most basic things I could think of.
What is the mass of 3.75 moles of NaCI? ( Na= 22.99g/mol, CI= 35.45 g/mol)
Answer:
219.15 grams
Explanation:
What is the mass of 3.75 moles of NaCI? ( Na= 22.99g/mol, CI= 35.45 g/mol)
Mole of Na = 22.99g
Mole of Cl = 35.45g
For NaCl we have ratio of 1:1, so we have 1 Na for every Cl
So we just add the two together to get the molar mass of NaCl which is
22.99 + 35.45 = 58.44g/mol
And we know we have 3.75 moles of NaCl so we multiply that by the molar mass of NaCl to get our answer
3.75 x 58.44 = 219.15grams
What occurs when potassium reacts with bromine to form potassium bromide?
1) Electrons are shared and the bonding is ionic.
2) Electrons are shared and the bonding is covalent.
3) Electrons are transferred and the bonding is ionic
4) Electrons are transferred and the bonding is covalent.
Which of the following viewed the atom as having a nucleus made up of protons and neutrons,with electrons orbiting the nucleus in fixed, stable orbits, much like the planets orbit the sun?
The correct answer is C. Bohr's model
Explanation:
Bohr's model of the atom developed in 1913 proposed each atom contained a nucleus with protons and neutrons. Also, there were electrons that orbited the nucleus. About this, Niels Bohr proposed the orbits of electrons were similar to those of planets around the sun; however, these did not occur due to gravity but to attraction forces. This model integrated new accurate ideas about the atom. However, this model was still inaccurate because particles in an atom are electrically charged and electrons do not orbit in fixed stable orbits and cannot be compared to the movement of planets around a star.
Answer:
Bohr's model
Explanation:
An unknown compound, B, has the molecular formula C7H12. On catalytic hydrogenation 1 mol of B absorbs 2 mol of hydrogen and yields 2-methylhexane. B has significant IR absorption band at about 3300 and 2200 cm-1. Which compound best represents B?
a. 5-methyl-1,3-hexadiene
b. 5-methyl-1-hexyne
c. 3-methyl-1-hexyne
d. 5-methyl-2-hexyne
e. 2-methyl-1,5-hexadiene
Answer:
B and D
Explanation:
If we use the info given we have a band a 3300 cm-1 and 2200 cm-1 this indicates that we have an alkyne functional group. Additionally, the hydrogenation of the unknown molecule will consume two moles of hydrogens this fits with the 2 pi bonds in the alkyne functional group. So, we can discard "a" and "e". The product of this hydrogenation is 2-methylhexane therefore we can discard c because the methyl group is placed on carbon 3. Structures b and d can work.
See figure 1
I hope it helps!
WILL GIVE BRAINLIEST!!!!! will give brainliest!!!!! ---------Write the molecular equation, complete ionic equation and net ionic equation of Barium nitrate reacting with potassium carbonate.
Answer:
Molecular:
Ba(NO3)2 + K2CO3 -> BaCO3 + 2KNO3
Complete ionic:
Ba2+ + 2NO3- + 2K+ + CO3 2- -> BaCO3 + 2K+ + 2NO3-
Net ionic:
Ba2+ + CO3 2- - > BaCO3
Explanation:
Molecular consists of all species reacting.
Complete ionic consists of all ionic species (ex. K+, NO3-) separated, as well as any compounds that didn't dissociate into ions (BaCO3 doesn't dissolve).
Net ionic doesn't include spectator ions (in this case, nitrate and potassium) and only species that aren't present on both sides of the arrow (barium and carbonate become a solid precipitate, so the ions aren't present as products, making them appear in the net ionic equation).
A student has an unknown sample of solution X. This solution is placed in a 1.00 cm wide cuvet and inserted into the spectrometer, producing an absorbance reading of 0.275 at a wavelength of 525.0 nm. What is the concentration of solution X in the unknown sample
Answer:
The concentration of the sample is 3.564x10⁻³M.
Explanation:
Using Lambert-Beer law, absorbance of a sample is directely proportional to its concentration.
The general graph of the absorbance of the standards with different concentrations is:
Y = 75.9X + 0.0045
R² = 0.9946
Where Y is the absorbance of the sample and X its concentration in mole/L.
If a solution has an absorbance of 0.275:
0.275 = 75.9X + 0.0045
0.2705 = 75.9X
3.564x10⁻³M = X → The concentration of the sample.
Which of the following is evidence for a physical change? A) burning B) fizzing C) evaporating D) rusting
Answer:c
Explanation: rusting, burning and fuzzing are all examples of chemical reactions/changes.
Which option describes a similarity and a difference between isotopes of an element? A. same atomic number; different number of protons B. same number of protons; different atomic number C. same atomic number; different mass number D. same mass number; different atomic number E. same number of neutrons; same number of protons
Answer:
c
Explanation:
what would happen if you place two positive charges next to each other and let go. would they attract, stay still, or they would repel
Answer:
they would repel
Explanation:
unlike charges attract while like ones repel.
carbon dioxide is a non-polar molecule true or false
Answer:
True
Explanation:
Due to the arrangement of the molecule, a carbon dioxide molecule is non-polar.