Answer:
4 sig fis so look at the next number which is "4"
answer is 19.97
all numbers not zeros are significant
Caffeine (C8H10N4O2) is a stimulant found in coffees and teas. When dissolved in water, it can accept a proton from a water molecule. Write the chemical equation for this process and identify the Brønsted-Lowry acid and base
Answer:
See figure 1
Explanation:
If we want to find the acid and the Brønsted-Lowry base, we must remember the definition for each of these molecules:
-) Acid: hydrogen donor
-) Base: hydrogen acceptor
In the caffeine structure, we have several atoms of nitrogen. These nitrogen atoms have the ability to accept hydronium ions ([tex]H^+[/tex]). Therefore the caffeine molecule will be the base since it can accept
If caffeine is the base, the water must be the acid. So, the water in this reaction donated a hydronium ion.
Thus, caffeine is the base and water the acid. (See figure 1)
In the reaction of caffeine with water, H₂O and C₈H₁₁N₄O₂⁺ are Brønsted-Lowry acids while C₈H₁₀N₄O₂ and OH⁻ are Brønsted-Lowry bases.
Caffeine reacts with water in an acid-base reaction. We want to identify acids and bases according to Brønsted-Lowry theory.
What is Brønsted-Lowry theory?It is a theory that classifies substances as acids and bases according to their behavior in a reaction.
An acid is a species that donates H⁺.A base is a species that accepts H⁺.The chemical equation for the acid-base reaction between caffeine and water is:
C₈H₁₀N₄O₂ + H₂O ⇄ C₈H₁₁N₄O₂⁺ + OH⁻
C₈H₁₀N₄O₂ accepts a H⁺ so it is a base while H₂O donates a H⁺ so it is an acid. This reaction is reversible, so we can also state that C₈H₁₁N₄O₂⁺ is an acid because it donates a H⁺ and OH⁻ is a base because it accepts a H⁺.
In the reaction of caffeine with water, H₂O and C₈H₁₁N₄O₂⁺ are Brønsted-Lowry acids while C₈H₁₀N₄O₂ and OH⁻ are Brønsted-Lowry bases.
Learn more about Brønsted-Lowry acid base theory here: https://brainly.com/question/7256753
Classify each of the following as either a physical change or a chemical change.
a. tearing a sheet of paper,
b. melting a piece of wax,
c. burning a log
Answer: A:Physical, B:Both, C: Chemical
Explanation:
Tearing paper is physical because only the appearance has changed. Melting wax can be either physical or chemical depending on whether the wax actually burns or not, burning a log is chemical because new substances are formed when wood burns.
The average adult heart pumps about 84./mLs of blood at 72 beats per minute. Suppose you need to calculate how long it would take the average heart to circulate 3600.mL of blood. Set the math up. But don't do any of it. Just leave your answer as a math expression. Also, be sure your answer includes all the correct unit symbols.
Answer:
42.857 seconds
Explanation:
Given that:
The average adult heart pumps about 84./mLs of blood at 72 beats per minute.
The total volume = 3600 mL
The objective is to calculate how long it would take the average heart circulate 3600 mL of blood.
Since 84 mL of blood takes 1 seconds to pump,
assuming q is the time required for heart to pump 3600 mL of blood
[tex]Time \ ( q )= \dfrac{3600 mL \times 1\ seconds}{84 \ mL}[/tex]
TIme (q) = 42.857 seconds
One of the differences between a voltaic cell and an electrolytic cell is that in an electrolytic cell __________.
Answer:
a nonspontanenous reaction is forced to occur
Hope this helps :)
The distance from earth to the star Proxima Centauri is 4.22 light years, which means it would take a ray of light 4.22 years to travel from earth to the star. How many miles separate earth and Proxima Centauri?
Answer:
2.48x10¹³ miles is the distance from the earth to Proxima Centauri
Explanation:
Light years is an unit of distance used in Astronomy. That is because 1 light year = 9.461x10¹²km; a real big distance used in the science that study the universe.
In km, 4.22 light years are:
4.22 light years * (9.461x10¹²km / 1 light year) = 3.9925x10¹³km
As 1 mile = 1.60934km, this distance in miles is:
3.9925x10¹³km * (1 mile / 1.60934km) =
2.48x10¹³ miles is the distance from the earth to Proxima CentauriHow can people conserve water at home? rinsing dishes with cool water instead of warm water
washing dishes only when the dishwasher is full
The central Xe atom in the XeF4 molecule has ________ unbonded electron pair(s) and ________ bonded electron pair(s) in its valence shell.
Answer:
Lewis structure in attachment.
Explanation:
Atoms of elements in and beyond the third period of the periodic table form some compounds in which more than eight electrons surround the central atom. In addition to the 3s and 3p orbitals, elements in the third period also have 3d orbitals that can be used in bonding. These orbitals enable an atom to form an expanded octet.
The central Xe atom in the XeF₄ molecule has two unbonded electron pairs and four bonded electron pairs in its valence shell.
The central Xe atom in the XeF4 molecule has 2 unbonded electron pair(s) and 4 bonded electron pair(s) in its valence shell.
Xenon is the element with the following electronic configuration:
[Kr] 4d¹⁰5s²5p⁶
As we can see there are 6 electrons in the p block of its outer orbitalit means Xenon has 6 bonding electron pairs, therefore the electron geometry of octahedraltwo of the pairs of electrons on the central atom are unbonded, or lone pairs therefore the molecular geometry is square planar.four pairs are bonded in its valence cell.Thus, The central Xe atom in the XeF4 molecule has 2 unbonded electron pair(s) and 4 bonded electron pair(s) in its valence shell.
Learn more:
https://brainly.com/question/18385138
What kind of molecular orbital would result when atomic orbitals are combined as indicated?
Provided question is incomplete as it lacks image or diagtram related to the question, however the correct indication is attach with answer :
Answer:
The correct answer is : antibonding molecular orbital
Explanation:
At the point when two atomic orbitals can consolidate directly produce two molecualr orbital, of which one is holding sub-atomic orbital of lower vitality and the other antibonding molecular orbital of higher energy.
Holding molecular orbital would by and large outcomes which nuclear orbitals of same phase joins while antibonding molecular orbital would results when atomic orbitals of various stages can combine.
In the given approach, it is obvious that one of S - orbital is going consolidate directly with opposite phase of p - orbital along their inter nuclear axis. Subsequently it prompts the formation of sigma antibonding molecular orbital.
Thus, the correct answer is : antibonding molecular orbital
Which three of the following statements accurately describe the blood buffering system in humans? The blood buffering system...
a) utilizes the H2CO3/HCO3^- conjugate acid/base pair.
b) maintains the pH of blood near 7.4.
c) regulates the blood pH at 7.4 +/- one pH unit.
d) depends on the ionization of H2PO4^-.
e) utilizes the acetic acid/acetate conjugate acid/base pair.
f) is facilitated by the enzyme carbonic anhydrase, which interconverts carbon dioxide and water to carbonic acid (ionizes into bicarbonate and H^+).
Answer:
b) maintains the pH of blood near 7.4.
c) regulates the blood pH at 7.4 +/- one pH unit.
f) is facilitated by the enzyme carbonic anhydrase, which interconverts carbon dioxide and water to carbonic acid (ionizes into bicarbonate and H^+).
Explanation:
The pH of human blood is slightly acidic i. e. 7.4. The enzyme carbonic anhydrase is responsible for the regulation to neutral and prevent it from acidic. the enzyme carbonic anhydrase helps in the conversion of carbon dioxide to carbonic acid and bicarbonate ions. When the blood reach to lungs, the bicarbonate ions convert back to CO2 and this carbondioxide is exhaled from the body.
Write the rate law for the following elementary reaction: H2(g) 2I(g) (g) Use to stand for the rate constant.
Answer:
rate = k ×[H₂] × [I]²
Explanation:
Write the rate law for the following elementary reaction: H₂(g) + 2 I(g) → 2 HI(g) Use k, to stand for the rate constant.
Step 1: Write the elementary reaction
H₂(g) + 2 I(g) → 2 HI(g)
Step 2: Write the rate law
The generic rate law is
rate = k ×[H₂]ᵃ × [I]ᵇ
where,
rate: reaction rate
k: rate constant
[H₂] and [I]: molar concentrations of the reactants
a and b: reaction orders for H₂ and I, respectively
For elementary reactions, the reaction orders coincide with the stoichiometric coefficients. Then, the rate law is:
rate = k ×[H₂] × [I]²
The bond angles in H3O are less than____________ and greater than_______.
Answer:
104.5 and 109.5
Explanation:
Bond angle is the angle formed between three atoms which has at least two bonds present between them. The number of lone pairs in a covalent bond is a determinant of the bond angle as the lone pairs which are negatively charged repulses the bond pairs thereby creating a distortion and angle.
Studies have however shown that the bond angles in H3O are lesser than 109.5 and greater than 103.5. This provides a bond range of H3O.
What type of bond forms in iron (II) chloride?
Explanation:
What type of bond forms in iron (II) chloride?
Ionic BondWhat types of knowledge and background did Underwood and Prescott bring to the problem?
Answer:
The answer is on the screenshot
Explanation:
Which type of phychologist would help to improve work productivity
Industrial and organizational psychologists study organizations and their employees to improve the productivity, satisfaction, safety, health and well-being of those within the workplace environment.
Your question has been heard loud and clear.
Well , work productivity is a necessity in all fields of science and businesses especially those dealing with commerce. So , for each of these fields , we have specific psychologists to help with work productivity.
Examples: Aviation Psychologists (Field of Aviation)
These psychologists study the behavior of pilots and other flight crew members. Aviation psychologists also perform research on airline safety, develop new training equipment, and help select suitable employees.
Biopsychologists (Field of biology)
These psychologists are also sometimes called biological psychologists or physiological psychologists. They study and perform research on the brain and behavior. By examining the neural bases of behavior, biopsychologists are able to understand different biological factors that might impact how people think, feel, and act.
Educational Psychologists (Field of education)
These psychologists study how people learn and the educational process. This might involve developing instructional strategies and teaching techniques. Some educational psychologists study giftedness or learning disabilities.
Thank you.
carbon dioxide at 25 degrees celsius and 101.3 kpa has a density of 1.799 kg/m^3 determine gas constant
Answer:
Explanation:
Temperature of gas in absolute scale T = 25 + 273 = 298 .
pressure of gas P = 1.013 x 10⁵ N / m²
density D = 1.799 kg / m³
= 1799 g / m³
From gas formula
PV / T = n R Where P is pressure , V is volume and T is absolute temperature , n is no of moles
P / T = n R / V
P / T = m R /M V where m is mass of gas and M is molecular weight .
m / V = D ( density )
P / T = DR/ M
PM / DT = R
Putting the values
1.013 x 10⁵ x 44 / (1799 x 298)
R = 8.314.09 J / K mole
In a cathode ray tube, electrons flow from the negatively charged cathode to the positively charged anode. Cathode ray tubes may be small and compact, but they typically must be plugged in to function. The flow of electrons within this tube is:________.
a. spontaneous
b. nonspontaneous
c. neither spontaneous nor nonspontaneous
d. impossible to tell
Answer:
spontaneous
Explanation:
Electrons in a cathode ray tube are produced at the cathode and move towards the anode which is the the positive electrode.
This flow of electrons is spontaneous because electrons flow from a point of negative electric potential to a point of positive electric potential, hence the answer above.
The solubility of silver sulfate (Ag2SO4), in moles per liter, can be expressed in terms of the resulting ion concentrations. Which relationship is correct?
Answer:
Solubility = [SO₄²⁻]
Explanation:
Solubility of Ag₂SO₄ can be determined by its ksp equilibrium:
Ag₂SO₄(s) ⇄ SO₄²⁻ + 2Ag⁺
Where 1 mole of silver sulfate dissolves producing 1 mole of sulfate ion and 2 moles of silver ion.
Solubility is defined as the amount of solid that can be dissolved per liter of solution.
The moles of Ag₂SO₄ dissolved are equal to moles of SO₄²⁻.
That means:
Solubility = [SO₄²⁻]1.72 g elemental arsenic combined with excess chlorine gas to form 4.17 g of the arsenic chloride compound. If the molar mass is between 180-200 g/mol, write the balanced equation for this synthesis process.
Answer:
As + 3/2 Cl₂ → AsCl₃
Explanation:
The reaction of the problem is:
As + Cl₂ → AsₐClₓ
The problem consist in determine a and x from the formula to write the balanced equation.
1.72g of As are (Molar mass: 74.92g/mol):
1.72g * (1mol / 74.92g) = 0.02296 moles of As are added to the reaction.
As molar mass of the arsenic chloride is between 180-200g/mol, the moles produced are between:
4.17g * (1 mol / 180g) = 0.0232
4.17g * (1 mol / 200g) = 0.0209
As moles of As are 0.02296 the most logic is than 1 mole of As produce 1 mole of the compound, that means the arsenic compound contains 1 mole in each formula:
As₁Clₓ: AsClₓ
And also, 0.02296 moles of AsClₓ are produced, the molar mass is:
4.17g / 0.02296mol = 181.62g/mol.
The atom of As weighs 74.92g/mol. The mass of the chlorides is:
181.62 - 74.92 = 106.70g/mol.
1 atom of Cl weighs 35.45g/mol:
106.70g/mol / 35.45g/mol = 3.0 atoms of Cl are in the chemical formula, that is:
AsCl₃
And the balanced equation for this synthesis is:
As + Cl₂ → AsCl₃
As + 3/2 Cl₂ → AsCl₃1.Calculate the frequency of a chemical shift at 1.25 ppm using a 400 MHz NMR spectrometer.A)1500 HzB)450 HzC)320 HzD)500 Hz
Answer:
D
Explanation:
Chemical shift is given as
Frequency/frequency of instrument
Let c = chemical shift
F = frequency
I = frequency of instrument
Chemical shift = frequency/frequency Instrument
1.25ppm = Frequency /400
We cross multiply to find frequency
Frequency = 400 x 1.25
Frequency = 500Hz
Option d is the answer since it is 500hz
For each of the following nuclei, determine the binding energy per nucleon (in MeV). (For all masses, keep six places beyond the decimal point when performing your calculations. Then round your final answer to at least three significant figures.)(a) 21 MeV (b) 4He MeV (c) 180 MeV (d) 23Na MeV
Answer: (a) BE = 1.112 MeV
(b) BE = 7.074 MeV
(c) BE = 7.767 MeV
(d) BE = 8.112 MeV
Explanation: Binding energy per nucleon is the average energy necessary to remove a proton or a neutron from the nucleus of an atom. It is mathematically defined as:
[tex]BE = \frac{\Delta m.c^{2}}{A}[/tex]
Where
Δm is a difference in mass known as mass defect
A is atomic mass of an atom.
Mass Defect is determined by:
[tex]\Delta m =Zm_{p}+(A-Z)m_{n} - m_{nuc}[/tex]
where:
Z is atomic number
[tex]m_{p}[/tex] is mass of proton
[tex]m_{n}[/tex] is mass of neutron
[tex]m_{nuc}[/tex] is mass of the nucleus
Mass of proton is 1.007825u.
Mass of neutron is 1.008665u.
The unit u is equal to 931.5MeV/c².
(a) 2H(deuterion): Given: Z = 1; A = 2; [tex]m_{nuc}[/tex] = 2.014102u
[tex]\Delta m =1(1.007825)+1(1.008665) -2.014102[/tex]
[tex]\Delta m =0.002388u[/tex]
[tex]BE = \frac{0.002388.c^{2}}{2}.931.5\frac{MeV}{c^{2}}[/tex]
BE = 1.112MeV
(b) 4He (Helium): Given: Z = 2; A = 4; [tex]m_{nuc}[/tex] = 4.002603
[tex]\Delta m =2(1.007825)+2(1.008665) -4.002603[/tex]
[tex]\Delta m =0.030377u[/tex]
[tex]BE = \frac{0.030377.c^{2}}{4}.931.5\frac{MeV}{c^{2}}[/tex]
BE = 7.074MeV
(c) 18O (Oxygen): Given: Z = 8; A = 18; [tex]m_{nuc}[/tex] = 17.999160
[tex]\Delta m =8(1.007825)+10(1.008665) -17.999160[/tex]
[tex]\Delta m =0.15009u[/tex]
[tex]BE = \frac{0.15009.c^{2}}{18}.931.5\frac{MeV}{c^{2}}[/tex]
BE = 7.767MeV
(d) 23Na (Sodium): Given: Z = 11; A = 23; [tex]m_{nuc}[/tex] = 22.989767
[tex]\Delta m =11(1.007825)+12(1.008665) -22.989767[/tex]
[tex]\Delta m =0.200288u[/tex]
[tex]BE = \frac{0.200288.c^{2}}{23}.931.5\frac{MeV}{c^{2}}[/tex]
BE = 8.112MeV
Larissa needs to make 500ml of 2.00 M NaCl. The molecular weight of NaCl is 58.44. How does she make 500ml of 2.00 M NaCl? Question 3 options: A) Measure 29.22g NaCl and dissolve it into 500ml water. B) Measure 29.22g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask. C) Measure 58.44g NaCl and dissolve it into 500ml of water. D) Measure 58.44g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask.
Answer:
D) Measure 58.44g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask.
Explanation:
2.00M NaCl is a solution that contains 2.00 moles of NaCl per liter of solution.
As you want to prepare 500mL = 0.500L of the solution you need:
0.500L * (2.00 moles / L) = 1.00 moles of NaCl are required to prepare the solution.
Now, to convert these moles to grams you must use Molar weight (58.44g/mol) as follows:
1 moles of NaCl * (58.44g / mol) = 58.44g of NaCl are required to dissolve in 500mL to prepare the 2.00M solution.
And right option is:
D) Measure 58.44g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask.-You can't top off a solution before dissolve all solute because it is possible the volume changes-
Answer:
D) Measure 58.44g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask.
Explanation:
I got it right in class!
Hope this Helps!! :))
round 77.616 to two significant figures
Answer:
The answer to the question is 78
Answer:
78
Explanation:
In rounding off to two, we consider the third digit. if it is more than five we ad one to the second digit otherwise we truncate.
in the case of 77.616, we add one to the second digit and truncate the rest.
Compare the following values:
1 grams vs. 10 decigrams
Determine if the values have the same numerical value. Explain your reasoning.
Answer:
1 Gram (g) is equal to 10 decigrams (dg).
Explanation:
this is because there is 0.1 grams in a decigram
In carbon NMR, the carbon atom of the carbonyl group in aldehydes and ketones has a chemical shift of about:
Answer:
Its a shift of about 200ppm
Explanation:
because we know that a chemical shift explains the resonating frequency of a particular nucleus in relation to its standard as in a magnetic field so that
carbonyl group in aldehydes and ketones is 200ppm
A piece of metal weighing 267.0 g is placed in a graduated cylinder containing 229.0 mL of water. The volume of water now reads 257.5 mL. From these data calculate the density of the metal. e provided box. A piece of metal weighing 267.0 g is placed in a graduated cylinder containing 229.0 mL of water. The volume of water now reads 257.5 mL. From these data calculate the density of the metal.
Answer:
9.368g/mL
Explanation:
The density is defined as the mass of a compound in a determined volume.
Based on Archimedes' law, the volume of the piece of metal is the difference between the volume of the water + the inmersed piece - the original volume of water. That is:
Volume of the metal:
257.5mL - 229.0mL = 28.5mL
As the mass of the metal is 267.0g; its density is:
Density:
267.0g / 28.5mL =
9.368g/mLYou are making a 0.2M solution of sodium acetate in the lab. Sodium acetate has a molecular mass of 82.03 g/mol. How many g of sodium acetate will you use if you are making 500mL of the solution
Answer: The answer can be found on CHEG
Explanation:
Fill in the blanks: Electrons are ___ in an ionic bond, whereas they are___ in a polar covalent bond, and ___ in a nonpolar covalent bond.
Answer:
The correct answer is "transferred; unequally shared; equally shared".
Explanation:
Ionic bonding occurs when a positively charged atom (cation) interacts with a negatively charged atom (anion). In ionic bonding, the cation transfers its electron to the anion. In polar covalent bonding, electrons are unequally shared. This means that the electrons spend more time in an atom than the other, which gives partial positive and negative charges to the atoms. On the other hand in nonpolar covalent bonding, the electrons are equally shared and no charges are created.
Why was 1990 an important year regarding air quality?
O The United States took first steps to keep the air clean.
O The United States created the Environmental Protection Agency.
Modifications and improvements were made to the Clean Air Act.
O Funding was established under the Clean Air Act to study air pollution.
Answer:
The United States took first steps to keep the air clean.
Explanation:
The US environmental protection agency was created in the year 1970 so this option is wrong.
November 15, 1990 however was a milestone in keeping the air clean, the signing f the amendments, the amendments set the stage for protecting the ozone layer, improving air quality and visibility.
The correct option is option A; The United States took first steps to keep the air clean.
Answer:
C. Modifications and improvements were made to the Clean Air Act.
Explanation:
The Clean Air act was originally established in 1970 and was concerned with the aim of protecting people and the environment in general from polluted air. Polluted air could cause different illnesses and environmental degradation.
The law was amended in 1990 in which modifications and improvements were made to the Clean Air Act. There was the need to reduce acid rain, toxic emissions which could deplete the ozone layer and cause varying respiratory illnesses in humans and to increase visibility.
The electron in the He+ ion is excited to the n = 2 principal state. What is the energy of the electron now?
Answer:
= -13.6 eV
Explanation:
E = -13.6 ÷ [tex]\frac{Z^{2} }{n^{2} }[/tex]
where n is the principal state
Z is atomic number
and E is energy in electron volts.
Given that n = 2 and Helium Z = 2
⇒ E = -13.6 ÷ [tex]\frac{2^{2} }{2^{2} }[/tex]
= -13.6 eV
I believe this is helpful and easy to follow.
Consider the reaction below. If the concentration of B decreases by 0.068 M, what will be the change in concentration for C? 3A(g)+4B(g)⇋5C(g)
Answer:
.085 M .
Explanation:
3A(g) +4B(g) ⇋ 5C(g)
4 moles of B reacts with A to form 5 moles of C
.068 moles of B will reacts with A to form 5 x .068 / 4 moles of C
Moles of C formed
= 5 x .068 / 4
= .085 moles .