Answer:
killer T-cell find and destroy infected cells that have been turned into virus-making factories
What does a negative AHf for a molecule mean?
A. Energy was added when the molecule changed phases.
B. Energy was added when the molecule was formed from its
elements.
C. Energy was released when the molecule was formed from its
elements.
O D. Energy was released when the molecule went through a phase
change.
SUBMIT
Option D I got it right
ANSWER: C (ENERGY WAS RELEASED WHEN THE MOLECULE WAS FORMED FROM ITS ELEMENTS.)
HOPE THE OTHER PERSON IS WRONG!
What is a covalent compound?
A.a compound with a metal and a nonmetal ion sharing valence electrons
B.stable group of multiple metal nuclei sharing valence electrons
C.a compound with nonmetal ions transferring valence electrons
D.a stable group of more than one type of atom bonded by bonding electron pairs
A covalent compound is a compound with a metal and a nonmetal ion sharing valence electrons (option A).
What is a covalent compound?A covalent compound is a molecule formed by covalent bonds, in which the atoms share one or more pairs of valence electrons.
Covalent bond is a type of chemical bond where two atoms are connected to each other by the sharing of two or more electrons.
Chemical compounds are generally grouped into one of two categories as follows;
covalent compounds ionic compoundsCovalent or molecular compounds generally result from two nonmetals reacting with each other. The elements form a compound by sharing electrons, resulting in an electrically neutral molecule.
Examples of covalent compounds are as follows:
watersucroseDNALearn more about covalent compounds at: https://brainly.com/question/11632372
#SPJ1
why is the volume of hydrogen is doubled the volume of oxygen in electrolysis of water?
Explanation:
As you can that water splits into molecules of hydrogen and 1 molecules of oxygen since , number of molecules of hydrogen released is double the number of molecules of oxygen released, volume occupied by hydrogen gas is double the volume occupied by oxygen gas
help with this........
An equinox occurs when the:
sun is farthest away from the equator
sun is directly over the equator
north pole is tilted away from the sun
south pole is tilted away from the sun
Answer: sun is directly over the equator
Explanation:
There are only two times of the year when the Earth's axis is tilted neither toward nor away from the sun, resulting in a "nearly" equal amount of daylight and darkness at all latitudes.
Please help!! only right answers!! will mark brainlest.
Answer:
7.35 *2
Explanation:
Because I mole of Na2o is made of 2 moles of NaOH
Why does water float on corn syrup
Answer:
density.
Explanation:
A cubic centimeter of water weighs 1 gram. Since a cubic centimeter of vegetable oil weighs less than 1 gram, oil will float on water. Corn syrup is more dense than water so 1 cubic centimeter of corn syrup weighs more than 1 gram. Therefore, corn syrup sinks in water.
Answer:
Click on the photo to see the full attachment
A scientist performs an investigation in which thermal energy is removed from a sample of a substance. When the substance begins to change from a gas to a liquid, the scientist measures the temperature of the substance. This temperature is the substance's
A. melting point
B. freezing point
C. evaporation
D. condensation
Which two properties define the critical point of matter in a phase diagram? A. mass and volume B. pressure and volume C. pressure and temperature D. density and temperature E. density and pressure
Answer:
C. pressure and temperature
Explanation:
For each substance, the conditions defining the critical point are the critical temperature, the critical pressure, and the critical density.
Hope this helped!!!
Pressure and temperature are the properties defining the critical point of matter in a phase diagram. The correct option is C.
What is a phase diagram?A phase diagram is a visualization of a material's physical states under various situations of pressure and temperature.
Pressure is on the y-axis of a typical phase diagram, and temperature is on the x-axis. A phase transition when we cross the lines or curves on the phase diagram.
The pressure and temperature point on a phase diagram where a material's liquid and gaseous phases merge into a single phase.
The merged single phase is known as a supercritical fluid above the critical point temperature.
Phase diagrams are graphical representations of the connections between the various phases that appear in a system under equilibrium conditions.
Thus, the correct option is C.
For more details regarding phase diagram, visit:
https://brainly.com/question/16945664
#SPJ2
Which elements have two electron shells?
Helium
Lithium
Done
B
Boron
Calcium
Oxygen
Lead
Nitrogen
Keep going
Answer:
Helium (He)
Lithium (Li)
Beryllium (Be)
Boron (B)
Explanation:
The chemical elements which have two (2) electron shells are: Lithium and Boron.
Valence electrons can be defined as the number of electrons present in the outermost electron shell of an atom. Thus, valence electrons is typically used to determine whether or not an atom or group of chemical elements found in a periodic table can form a chemical bond with others.
This ultimately implies that, valency is a property that is typically used in determining the chemical properties of chemical elements.
An electron shell can be defined as the outermost shell of an atom around the atomic nucleus. Thus, it is considered to be an orbit accompanied by electrons around the nucleus of an atom.
In Chemistry, the chemical elements which have two (2) electron shells are:
Lithium: it has two electrons in its first shell and one electron in its second shell. Boron: it has two electrons in its first shell and three electrons in its second shell.Read more: https://brainly.com/question/18214726
How many grams of water, H 2 O , is given o when 62.1 g of propane, C 3 H 8 , burns?
Answer:
101.62 grams of water is given o when 62.1 g of propane burns.
Explanation:
Propane gas (C₃H₈) burns with oxygen gas and products carbon dioxide gas and liquid water. The balanced reaction is:
C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O
By stoichiometry, the following amounts of moles of each compound participate in the reaction:
C₃H₈: 1 mole O₂: 5 moles CO₂: 3 moles H₂O: 4 molesBeing the molar mass of each compound:
C₃H₈: 44 g/mole O₂: 32 g/moleCO₂: 44 g/moleH₂O: 18 g/moleBy stoichiometry, the following mass quantities of each compound participate in the reaction:
C₃H₈: 1 mole* 44 g/mole= 44 grams O₂: 5 moles* 32 g/mole= 160 gramsCO₂: 3 moles* 44 g/mole= 132 gramsH₂O: 4 moles* 18 g/mole= 72 gramsThen you can apply the following rule of three: if by stoichiometry 44 grams of propane produces 72 grams of water, 62.1 grams of propane how much mass of water does it produce?
[tex]mass of water=\frac{62.1 grams of propane*72 grams of water}{44 grams of propane}[/tex]
mass of water= 101.62 grams
101.62 grams of water is given o when 62.1 g of propane burns.
A gas confined in a 515cm3 container exerts a pressure of 107.4kPa at 38.6⁰C. At what Celsius temperature will it exert a pressure of 635.7kPa if it is placed into a 644cm3 container?
Answer: The temperature at pressure of 635.7 kPa is [tex]2033^0C[/tex]
Explanation:
The combined gas equation is,
[tex]\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}[/tex]
where,
[tex]P_1[/tex] = initial pressure of gas = 107.4 kPa
[tex]P_2[/tex] = final pressure of gas = 635.7 kPa
[tex]V_1[/tex] = initial volume of gas = [tex]515cm^3[/tex]
[tex]V_2[/tex] = final volume of gas = [tex]644cm^3[/tex]
[tex]T_1[/tex] = initial temperature of gas = [tex]38.6^0C=(38.6+273)K=311.6K[/tex]
= final temperature of gas = ?
Now put all the given values in the above equation, we get:
[tex]\frac{107.4\times 515}{311.6}=\frac{635.7\times 644}{T_2}[/tex]
[tex]T_2=2306K=(2306-273)^0C=2033^0C[/tex]
The temperature at pressure of 635.7 kPa is [tex]2033^0C[/tex]
does adding acid make a solution more acidic or basic
Answer:
Adding an acid increases the concentration of H3O+ ions in the solution. Adding a base decreases the concentration of H3O+ ions in the solution. An acid and a base are like chemical opposites. If a base is added to an acidic solution, the solution becomes less acidic and moves toward the middle of the pH scale.
Difference between Displacement and Double Displacement reaction
Answer:
please follow me
Explanation:
A displacement reaction is the one when a more reactive substance displaces a less reactive one from its salt solution whereas a double displacement reaction is the one where a mutual exchange of ions happens between two compounds.
What happens when Sulphuric acid is added into Barium Chloride solution?
Answer:
white precipitate of barium chloride is formed
WILL MARK BRAINLIEST
Answer:
B) inertia
Explanation:
Sorry if wrong
What does pH measure?
A. the density of a solution
B. the salt concentration of a solution
C. the sulfate ion concentration of a solution
D. the hydronium ion concentration of a solution
Answer:
Option D
Explanation:
Hydronium ion concentration is a measure of pH of a solution.
The mathematical equation for the same is [H3O+] = 10-pH
OR
[H3O+] = antilog (- pH)
Hence, option D is correct
which non metal is a good conductor of heat and electricity ?
Answer:
Graphite
Graphite is a non-metal and it is the only non-metal that can conduct electricity. You can find non-metals on the right side of the periodic table and graphite is the only non-metal that is a good conductor of electricity.
Answer:
Graphite is a non metal which is a good conductor of heat and electricity .
hope it is helpful to you
In the combustion of octane, 2 C8H18 +25 O2 --> 16 CO2 + 18 H2O, if 376.0 liters of carbon dioxide formed at STP, then the volume of oxygen used was A. 587.5 L B. 240.6 L C. 839.3 L D. 299.1 L
Answer:
587.5 L (Option A)
Explanation:
The reaction is:
2 C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O
We know that in STP conditions 1 mol of any gas is contained in 22.4L
Then, we can make a rule of three, to determine the moles of produced carbon dioxide.
22.4L is the volume for 1 mol
376 L will be the volume for (376 . 1) 22.4 = 16.78 moles at STP conditions.
Stoichiometry is 16:25.
16 moles of CO₂ are produce by the reaction of 25 moles of O₂
Then, 16.78 moles of CO₂ were produced by (16.78 . 25) /16 = 26.2 moles.
Now, the rule of three again.
1 mol of oxygen gas is contained at 22.4L, at STP conditions
26.2 moles might be contained at (26.2 . 22.4)/1 = 587.5 L
How do you determine if an equation is balanced or unbalanced.
The combustion of ethene,C2H4,is an exothermic reaction. Use the information below to determine the amount of energy given off when 1000g of ethene is conbusted C2H4+3 O2-> 2CO2 + H20
Answer:
[tex]Q=-50,307kJ[/tex]
Explanation:
Hello there!
In this case, since following reaction:
C2H4+3 O2-> 2CO2 + 2H2O
Has an enthalpy of combustion of ethene is about -1411.1 kJ/mol (can be found on goo gle), it is possible to calculate the total amount of energy that is released when 1000 grams of ethene are burned as shown below:
[tex]Q=-1411.1 \frac{kJ}{molC_2H_4} *\frac{1molC_2H_4}{28.05gC_2H_4}*1000gC_2H_4 \\\\Q=-50,307kJ[/tex]
Best regards!
please help this is very important
Answer:
B
Explanation:
How many moles of oxygen are required to react completely with 5.00 grams of hydrogen?
Answer:
3
Explanation:
What is the specific heat of silicon if the temperature of a 4.11 g sample of silicon
is increased by 3.8 °C when 11.1 J of heat is added?
Answer:
The right solution is "0.7107 J/g°C".
Explanation:
The given values are:
Mass,
m = 4.11 g
Temperature,
ΔT = 3.8°C
Heat,
Q = 11.1 J
The specific heat of silicon will be:
⇒ [tex]C=\frac{Q}{m \Delta T}[/tex]
On substituting the values, we get
⇒ [tex]=\frac{11.1}{4.11\times 3.8}[/tex]
⇒ [tex]=\frac{11.1}{15.618}[/tex]
⇒ [tex]=0.7107 \ J/g^{\circ}C[/tex]
which statement best describes a chemical property related to the particles that make up a material
A. nickel is a good conductor of electricity because the metallic bonds between its atoms allow electrons to move freely.
B. demand is a hard substance because its atoms are joined together by covalent bonds.
C. metallic bonds between its ions cause silver to be a highly malleable material.
D. chlorine is highly reactive with other elements because its atoms have 7 valence eletrons.
The statement that best describes a chemical property related to the particles that make up a material is A) nickel is a good conductor of electricity because the metallic bonds between its atoms allow electrons to move freely. Option A
Chemical properties describe how substances undergo chemical reactions or interactions with other substances. In this case, the statement about nickel highlights a specific chemical property related to its ability to conduct electricity.
Nickel is a metallic element with a unique atomic structure. It possesses metallic bonds, which involve the sharing of electrons between atoms within a metal lattice. In metallic bonding, the valence electrons of metal atoms are delocalized, meaning they are not strongly associated with any specific atom but are free to move throughout the material.
The presence of these mobile electrons in nickel enables it to conduct electricity effectively. When a potential difference is applied across a conductor like nickel, the mobile electrons can move in response to the electric field, carrying electrical charge from one point to another.
Option B) is incorrect because hardness is a physical property related to the arrangement and bonding of atoms, not a chemical property.
Option C) is also incorrect because malleability is a physical property resulting from the ability of metal atoms to slide past each other when a force is applied, not a chemical property.
Option D) describes the electronic configuration of chlorine, which is a characteristic of its atom but does not directly relate to a chemical property associated with the particles that make up a material.
In summary, option A best describes a chemical property related to the particles that make up a material, specifically nickel's ability to conduct electricity due to the presence of mobile electrons enabled by metallic bonds.
Option A
For more such quetsion on chemical property visit:
https://brainly.com/question/29886197
#SPJ8
61 Cu
29
Write the complete nuclear equations for alpha absorption
Answer:
⁶¹₂₉Cu + ⁴₂He --->⁶⁵₃₁Ga
Explanation:
Nuclear reactions are reactions which occur with changes in the nucleus of an atom. Nuclear reactions usually occur with the release of large amounts of energy and radiation. Radiactive elements are elements that are involved in nuclearbreactions due to the unstable nature of their nucleus. They disintegrate spontaneously with the emission of radiations. The major types of radiations released during nuclear reactions are;
1, Alpha particles - these are positively charged radiations with strong ionizing power. Each alpha particle is a helium nucleus
2. Beta particles - these are very fast moving stream of electrons. They are negatively charged particles .
3. Gamma radiation - is a form of electromagnetic radiation.
In the alpha absorption of Cu-61, the proton number of the atom increases by 2 while the mass number increases by 4 and the Cu-61 atom is changed to Ga-65 atom. The nuclear equation is given as follows:
⁶¹₂₉Cu + ⁴₂He --->⁶⁵₃₁Ga
which of these phenomena cause uneven heating of the earth
Land and water have different heat capacities
Land and water have the same rate of heat absorption
The angle of incoming sunlight varies at different places
Air travels from areas of low pressure to areas of high pressure
Winds blow in the same direction across Earth's Surface
Answer:
The angle of incoming sunlight varies at different places
Answer: This answer is multiple choices.
1. Land and water have different heat capacities.
And
3. The angle of incoming sunlight varies at different places.
Explanation: I kept seeing other people only putting in one answer, so I used this answer from someone else. Credit to them!
Identify the pair in whic 1 the formula does not match the name
sulfite, SO32
nitrite, NO3-
hydroxide, OB
dichromate, C 20-2
Answer:
hydroxide is the one because it is the one HAHAH
Answer:
hydroxide, OB
Explanation:
hydroxide,OB
calculate the molarity of 0.57 moles NaHCO3 in 61.2 mL of solution. Report your answer 4 places after the decimal don’t forget to round.
Answer:
The correct response is "9.313 M".
Explanation:
According to the question, the values are:
Moles of solute,
= 0.57 moles
Liters of solution,
= 61.2 mL
or,
= 0.0612 L
Now,
The molarity will be:
= [tex]\frac{Moles \ of \ solute}{Liters \ of \ solution}[/tex]
On putting the given the values in the above formula, we get
= [tex]\frac{0.57}{0.0612}[/tex]
= [tex]9.313 \ M[/tex]
Which statement describes ionic bonds?
A) a lattice of ions in a sea of electrons.
B) electrostatic attraction between oppositely charged ions.
C) the sharing of electrons between atoms to gain a noble gas configuration.
D) the transfer of electrons from atoms of a non-metal to the atoms of a metal.