Answer:
a
Explanation:
equatinal by elimination melha
8n-3y = 18 and5x+6y=27
Answer:
x = 3 and y= 2
Explanation:
Given equations:
8x - 3y = 18 - ---- (I)
5x + 6y = 27 -------(II)
Solve this problem by elimination;
In the elimination method, we simply find a common term that can make one of the variables in the two equation the same. Then we either add or subtract to remove the variable.
Mulitply equation (i) by 5 to give equation III
Mulitply equation (II) by 8 to give equation IV
5(8x - 3y) = 5(18) ------- III
8(5x + 6y) = 8(27) ------- IV
40x - 15y = 90------- III
40x + 48y = 216 ------- IV
Subtract equation III and IV;
-15y - 48y = 90 - 216
- 63y = -126
y = 2
Solve for x;
40x - 15y = 90;
40x - 15(2) = 90
40x - 30 = 90
40x = 90 + 30
40x = 120
x = 3
What happens when you add salt to very cold ice?
Which two substances are among the four major types of organic compounds made by living things?
A. Lipids
B. Carbon dioxide
C. Water
D. Nucleic acids
Answer:
I think carbon.
Explanation:
............
Please help
The charge of o monatomic ion is its oxidation number.
O True
O False
O Neither
name two diffirent kinds of animals and identify at least one characteristic that makes them diffirent from each other
Answer:
Bears and Whales
Explanation:
Bears keep themselves warm via a thick fur coat
Whales keep themselves warm with a thick layer of blubber
is Mo2S6 ionic or covalent
Answer: Ionic
Explanation:
Answer:
ionic
Explanation:
When many earthquakes are studied, there is another common pattern that emerges: a "Shadow Zone". This is an area, for any earthquake, on the Earth where direct S-waves don't arrive at all and P waves are refracted. What do you think causes these P waves to be refracted? *
Answer:
Sudden decrease in the velocity at the boundary.
Explanation:
The shadow zone is the zone of the earth from angular distances of 104° to 140° from a known earthquake that does not directly receive any P waves. Now, this shadow zone occurs as a result of S waves getting stopped completely by the liquid core and the P waves being refracted by the liquid core.
From earlier seismic discoveries, this boundary which is the shadow zone that does not directly receive any P-waves was found to be due to the fact that the P-waves were refracted inwards as a result of the sudden decrease in velocity at the boundary.
If the density of a substance is 2.18 g/mL, how would you find the density given that the mass is 0.987 kg and the volume is 4.52 x 102 mL?
Answer:
Explanation:
Convert mass in gms .. 987 gms
Density = mass/ volume
= 987/4.52 x102
= 2.18 g/mL
The modern synthesis combined the concepts of _______ and evolution.
Answer:
genetics
hope this helps :)
Explanation:
what is a covalent bond? Apex
Answer:
Here is the meaning of covalent bond: covalent bond: a chemical bond in which two atoms share some of their valence electrons which creates a force that holds the atoms together
Hope this helps
Sky
A chemical bond in which two atoms share some of their valence electrons creates a force that holds the atoms together.
What is a covalent bond?A covalent bond consists of the mutual sharing of one or more pairs of electrons between two atoms.
Covalent bonds have high bond dissociation energy as compared to the ionic bond. The overlapping of molecular orbital is bigger in the case of the covalent bonds as compared with ionic bonds.
Hence, covalent bonds are difficult to break and stronger than ionic bonds.
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Chemistry Data Analysis --
7.86 x 10^-15 x 3.9 x 10^-10
Answer:
3.065 x 10^-24
Explanation:
hope this helps
is muriatic acid a compound or not?
Which phrase is most similar in meaning to “scientific theory”?
A. a best guess explanation
B. a rigorously tested explanation
C. an opinion of what should happen
D. a mathematical relationship
Answer:
c
Explanation:
Answer:
A. a best guess explanation
Explanation:
A scientific theory explains why something behaves the way it does and is usually backed up by different sources. They are not speculations and can be proven. Those which are speculations and are not proven are called hypothesis. A scientific theory can also be replaced, if it is found that it does not produce valid results, or if a better theory is proposed which is made of one or more old theories.
Displacement is called vector quantity. Why?
Answer:
Distance is a scalar quantity that refers to "how much ground an object has covered" during its motion. Displacement is a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position.
Explanation:
I need help with the 2nd part first gets brainlist
Answer:
7. 4H₂O
Elements: Hydrogen, Oxygen
Number of molecules: 4
Number of elements: 8 H, 4 O
Number of Atoms: 12
Explanation:
The elements are determined by the their symbol i.e. H = hydrogen.
The number of molecules is determined by the coefficient ( the number in front of everything, in this case 4).
The number of elements is determined by the coefficient and the subscripts. Multiply the coefficient by the subscript after each element. When there is no subscript, it is equal to 1. 4H₂ = 4x2 = 8; 4O = 4x1 = 4.
The number of atoms is all the individual elements added together. 8+4 = 12.
Why are forecasters able to make more accurate predictions about the weather when using electronic tools?
O A wide variety of devices can be used to collect weather data from many places
O Weather data come exclusively from different weather stations in one region.
Data fed into a supercomputer accounts only for select processes that occur on Earth.
Scientists must input several pieces of weather information into a computer system.
Answer:
option 1
Explanation:
Forecasters, able to make more accurate predictions about the weather when using electronic tools because a wide variety of devices can be used to collect weather data from many places. Therefore, option A is correct.
What is forecaster ?Forecaster behavior is examined by forecasters to see how social, cultural, ethical, and environmental trends will likely impact it. They can determine what goods and services people will be wanting to purchase through this approach.
A person who informs you about the anticipated state of a situation: an analyst of the economy. a forecaster of weather. The term "meteorologist" has now become widely used to refer to someone who forecasts the weather and investigates objects that fall from the sky.
Fitzroy developed charts to allow forecasts to be made, which he called "forecasting the weather," and therefore created the word "weather forecast," after a storm in October 1859 that resulted in the loss of the Royal Charter.
Thus, option A is correct.
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Which types of matter are made of atoms
a. Mixtures
b. Elements
C. Compounds
D. All of the above
Answer:
D all above yes I think it's all above
Answer: D
Explanation: All of the above.
Plz mark brainliest:)
A student compared some chemical and physical properties of three pure substances. Her
data are recorded in the chart above. What is a logical conclusion the student can draw
about hare substances?
Pure substances have the same chemical and physical properties.
Pure substances have the same chemical properties, but different physical properties.
O Pure substances have the different chemical properties, but the same physical properties.
O Pure substances have different chemical and physical properties.
Answer:
letter b not c
Explanation:
next time please take a picture lucky i already took this
What is the mass of 4.49 x 10º carbon dioxide, CO2, molecules?
Is a backpack a good resource
for a rescue team?
what causes the tides
Answer:
Gravity causes tides
Explanation:
(Please try to answer my most recent question!!!!!)
Which pair of symbols represents nuclei with the same number of neutrons?
A. 56 Co and 580
B. 57Co and 58Ni
c. 57Fe and 58 Ni
D. 57Mn and 57Fe
Answer:
B
Explanation:
Mass number = number of neutrons + number of protons
Atomic number is the number of protons in the nucleus.
58Ni : 58 is the number of neutrons + number of protons
atomic number of Ni is 28. Thus, 58 -28 = 30 neutrons
57Co ; 57 is the number of neutrons + number of protons
number of Co is 27. Thus, 57 – 27 = 30 neutrons
where is lithium used in the body?
Answer:
Lithium is a naturally occurring alkali metal, which living organisms ingest from dietary sources and which is also present in trace amounts in the human body. In much higher concentrations, lithium is effective as a medication for mania and mood swings including manic depressive disorders
The density of air at STP is 1.285 g/L. Which of the following cannot be used to fill a balloon that will float in air at STP?
NO can't be used to fill a balloon
Further explanationConditions at T 0 ° C and P 1 atm are stated by STP (Standard Temperature and Pressure). At STP, Vm is 22.4 liters/mol.
Answer options that need to be added :
a. Ne
b. NO
c. NH₃
d. CH₄
e. HF
will float in air ⇒ element or compound to fill the balloon, its density must be less than < 1.285 g/L
We can use the ideal gas formula ta find density :
[tex]\tt \rho=\dfrac{P.MW}{RT}[/tex]
Because at STP, then the constant value is
[tex]\tt \rho=\dfrac{1~atm\times MW}{0.08205\times 273.15~K}\\\\\rho=0.0446\times MW[/tex]
So that the density is determined from the MW(molecular weight) of each element or compound
a. NeAr = 20.1797 g/mol
[tex]\tt \rho=0.0446\times 20.1797=0.9~g/L[/tex]
b. NOMW=30.006 g/mol
[tex]\tt \rho=0.0446\times 30.006=\boxed{\bold{1.338~g/L}}[/tex]
c. NH₃MW=17.0306 g/mol
[tex]\tt \rho=0.0446\times 17.0306=0.760~g/L[/tex]
d. CH₄MW=16.04 g/mol
[tex]\tt \rho=0.0446\times 16.04=0.715~g/L[/tex]
e. HFMW=20.01 g/mol
[tex]\tt \rho=0.0446\times 20.01=0.892~g/L[/tex]
What is Mercury's proximity to the sun
PLEASE HELPP
Answer:
46.943 million km
Explanation:
From an average distance of 36 million miles (58 million kilometers), Mercury is 0.4 astronomical units away from the Sun.
From an average distance of 36 million miles (58 million kilometres), Mercury is 0.4 astronomical units away from the Sun.
(I hope this helped ^^)
Which term describes weathering?
breaks down rock
causes heating and cooling
makes pebbles and rocks larger
carries away fragments
Answer:
Breaks down rocks.
Explanation:
Weathering is the breaking down of rocks often with water. For example a sea shell will get batered with water and over time form sand.
How much space does 2 x 10^22 atoms of copper take up?
Answer:
2.35mL
Explanation:
The amount of space a substance holds is its volume.
Density = mass (g) /volume (L)
Where;
mole = mass/molar mass
Since 1 mol of Cu contains 6.022 × 10^22 atoms.
There are 2 x 10^22/6.022 × 10^22 moles in 2 x 10^22 atoms of copper
2 x 10^22/6.022 × 10^22
2/6.022 × 10^(22-22)
0.332 × 10^0
0.332mol
Mole = mass/molar mass
0.332 = mass/63.5
mass = 63.5 × 0.332
mass = 21.08g
Density = mass/volume
Density of copper (Cu) is 8.96 g/cm³
8.96 = 21.08/v
V = 21.08/8.96
V = 2.35mL or cm³
Which group of atomic models is listed in historical order from the earliest to the most recent?
The historical order of atomic models from the earliest to the most recent is as: Hard sphere model, electron shell model, and wave mechanical model. Therefore, option (A) is correct.
What is the atomic model?The atomic model can be described as the model used to describe the structure and composition of the atom. The atom as a primary component of matter has been under extensive study to understand the universe.
In the classical model of an atom, the atom is made of smaller particles with an electrical charge called electrons, protons, and neutrons. To understand the atomic models, it is important to understand how these particles make up the atom.
There are five principal atomic models that have been proposed over time, which are Dalton’s atomic model, Thomson’s atomic model, Rutherford’s atomic model, Bohr’s atomic model, and the quantum atomic model.
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Your question was incomple, most probably the complete question was,
Which group of atomic models is listed in historical order from the earliest to the most recent?
A) Hard sphere model, electron shell model, and wave mechanical model
B) Hard sphere model, wave mechanical model, and electron shell model
C) Electron shell model, Hard sphere model, and wave mechanical model
D) Electron shell model, wave mechanical model, and Hard sphere model
List the steps of how a virus is able to infect your cells
Answer:
Key Points
Viral replication involves six steps: attachment, penetration, uncoating, replication, assembly, and release.
During attachment and penetration, the virus attaches itself to a host cell and injects its genetic material into it.
During the Metric Olympics yesterday, Molly's long jump was 118.3 cm. Christy accidentally recorded her results in inches. She jumped 51.18 inches. Can you help... Who won the long jump? Christy won by about 30 cm Christy won by about 30 cm Molly won by about 25 cm Molly won by about 25 cm Christy won by about 12 cm Christy won by about 12 cm Molly won by about 10 cm
Answer: Christy won Molly by 12cm
Explanation:
Ist step
Molly's ;ong jump was 118.3cm
Christy long jump was 51.18inches
2nd Step
we change christy score to cm so we can compare
1 inch = 2.54cm.
therefore 51.18 inches = 51.18 x 2.54= 129.9972cm
Christy won molly by 129.9971cm-118.3cm=11.69 rounded to 12cm
Christy won Molly by 12cm