You have a radioactive isotope with a mass of 400 grams. The sample has a half life of 5 days. How much is left after 25 days have passed?
Answer:
Amount left after 25 days = 12.5 g
Explanation:
Given data:
Mass of sample = 400 g
Half life of sample = 5 days
Mass left after 25 days = ?
Solution:
First of all we will calculate the number of half lives passes in given time period.
Number of half lives = Time elapsed / Half life
Number of half lives = 25 days/ 5 days
Number of half lives = 5
At time zero = 400 g
At 1st half life = 400 g/2 = 200 g
At 2nd half life = 200 g/2 = 100 g
At 3rd half life = 100 g/2 = 50 g
At 4th half life = 50 g/2 = 25 g
At 5th half life = 25 g/2 = 12.5 g
What is the element Ar classified as in the periodic table?
A- a noble gas
B- a halogen
C- a metalloid
D- a metal
The elements are the basic units that are indivisible and are defined by protons. The element Ar is classified as a noble gas in the periodic table. Thus, option A is correct.
What is a noble gas?Noble gas occupies the zero group in the periodic table and is unreactive and monoatomic gas that shares similar properties of being colorless, and odorless.
The gases helium, argon, neon, xenon, and krypton are noble gases that are inert, stable, and have low reaction rates that make them used in standard conditions.
The seven noble gases are unable to bond with the atoms of the other elements which makes them less reactive. Because of their less reactive nature, they are also called inert gases.
Therefore, argon (Ar) is a noble gas.
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Help you’ll get 12 points
Answer:
a
a
b
a
b
Explanation:
hope this is right! hope it helps :)
The molar mass of sodium of chloride
Answer:
22.989769 u.
Explanation:
pls vote.......
Answer:
58.44 g/mol
(extra words because i cant send it with less then 20 words or something like that)
What is an ore? An object that has been recycled, an article of clothing that’s made from natural fiber, a rock that contains enough of a metal to be worthwhile to extract, and a fossil fuel that can be burned to generate electricity.
Answer:
cccccccc
Explanation:
got it right
how are dogs born? (10 points)
Answer:
Most puppies are born head first but some come tail first. Puppies are born inside a thin sac, which the mother will remove, enabling them to breathe. After each puppy, your dog should pass an afterbirth (placenta), which they often eat.
Explanation:
Which element will never react, neon (Ne) or hydrogen (H)?
Answer:
Neon(Ne)
Explanation:
Neon will not react because it is a noble gas and had 8 electrons.
Answer:
Neon
Explanation:
Neon has a full octet and is a noble gas, hydrogen can still react because it can share or give its electron to another element
Calculate the speed.
1. If a car travels 800m in 30 seconds how fast is it going?
Answer:
s = 26.7 m/s
Explanation:
Given data:
Distance travel = 800 m
Time taken = 30 sec
Speed of car = ?
Solution:
Formula:
S = d/t
s = speed
d = distance
t = time
by putting values.
s = 800 m/ 30 s
s = 26.7 m/s
Whats the most common chemical element in the earths crust?
Answer:
Oxygen
Explanation:
it is 47% of the earth's crust.the 2nd would be silicon if you wanted to know.
have a good day maam!
initial consentretion
What is initial concentration?
High initial concentration of spilled oil has a negative effect on the biotransformation process that causes a significant lag phase of about 2–4 weeks. Even after biostimulation, at least a week is needed for microorganisms to adapt and the entire bioremediation process may require months and even years to be completed (Atlas, 1995; Zahed et al., 2010a). The rates of uptake and mineralization of many organic compounds by a microbial population depend on the concentration of the compound (Olivera et al., 1997; Rahman et al., 2002).
(03.07 LC)
What type of organic compound contains a nitrogen atom bonded to one, two, or three carbons
Answer:
Amines
Explanation:
The organic compound which contains nitrogen atom bonded to one, two or three carbons are the amines.
Amines are known to show an appreciable level of basicity. They are often regarded as the derivatives of ammonia that where one or two or three hydrogen atoms have been replaced by alkyl or aryl groups. Amines are classified into primary, secondary and tertiary on the basis of the number of substituted hydrogen atoms.
A sample of a fluid has a mass of 10g and volume of 2 ml. What is the density of this fluid?
A. 10 g/ml
B. 20 g/ml
C. 5 g/ml
D. 2 g/ml
Answer:
Is the letter C
Explanation:
You have to divide the mass with the volume
According to the principle of superposition, which statement is true about the sediment layers shown here?Required to answer. Single choice.
(20 Points)

A. Layer 2 is young relative to layer 3.
B. Layer 3 is young relative to layers 1, 2, and 4.
C. Layer 4 is old relative to layers 1 and 2.
D. Layer 2 is old relative to layers 3 and 4.
whoever gets it right gets 10pts
if layer 4 is at the very bottom it would be c
How can the shape of a molecule determine its polarity.
Answer:
The shape of the molecule will determine the direction of each of the individual bond dipoles, and thus, will always play a role in determining the polarity of the molecule as a whole.
Try to see if your answer is correct from that :)
Explanation:
When one side of a molecule (or polyatomic ion) is more positive (or negative) than the other, the molecule is said to be polar. The correct option is C.
Thus, When the bonds' polarities do not balance out, this happens.
As opposed to CO2, which is a nonpolar molecule, each carbon-oxygen link in CO2 is polar.
Due to the linear nature of the molecule, the two bonds point in different directions.
Their opposite polarities cause their effects to cancel. The molecule's two sides are equal; neither is more adverse than the other.
Thus, When one side of a molecule (or polyatomic ion) is more positive (or negative) than the other, the molecule is said to be polar. The correct option is C.
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Hydrogen atoms do not repel each other within a star
How many atoms in:
1. PbF3 -
2. Pb2O3 -
Answer:
The correct answer is 1) 257 and 2) 135
Explanation:
Ultrasound and Magnetic Resonance Imaging (MRI), are technologies used to create images of a patient's internal features. In many instances, either technology can be used when diagnosing patients. However, ultrasound is often preferred for diagnosing moving features, while MRI is often preferred for diagnosing features surrounded by air or dense bone. Based on these differences, which of the following best describes the waves used by these technologies?
A.
Ultrasound uses sonar technology with sound waves, while MRI uses electromagnetic waves.
B.
Ultrasound and MRI both use electromagnetic waves because electromagnetic waves require a medium through which to travel.
C.
Ultrasound and MRI both use sonar technology with sound waves because sound waves are not affected by a change in medium.
D.
Ultrasound uses electromagnetic waves, while MRI uses sonar technology with sound waves.
Ultrasound uses sonar technology with sound waves while MRI uses electromagnetic waves.
What are electromagnetic waves?
The electromagnetic radiation consists of electromagnetic waves made up of electromagnetic field which are capable of propogating through space and carry the radiant electromagnetic energy.
The radiation are composed of electromagnetic waves which are synchronized oscillations of electric and magnetic fields . They are created due to change which is periodic in electric as well as magnetic fields.
In vacuum ,all the electromagnetic waves travel at the same speed that is with the speed of air.Ultrasound uses sonar technology with sound waves while MRI uses electromagnetic waves.There are seven type of electromagnetic waves depending on the energy and frequency of the waves. These waves are a solution of Maxwell's equation.
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help please this is due soon!!
Answer:
33
Explanation:
what is the balanced equation for Na+F2-NaF
Based on the kinetic theory, which statement is true? (1 point)
Matter consists of only large molecules.
Matter is made up of only charged particles.
The particles of matter are in constant motion.
The particles of matter have zero kinetic energy.
Answer:
the particles of matter are in constant motion.
Explanation:
How many atoms will there be in 5.00 g of gold. (Use ^ to show the exponent in scientific notation. For example, 4 X 1011 should be written 4 X 10^11. Include the unit "atoms" in your answer.
Answer:
1.53x10^22 atoms of Au
Explanation:
To find the atoms of gold we need first, to convert the mass of gold to moles using molar mass of gold (196.97g/mol). Then, these moles must be converted to number of atoms based on definition of moles (1 mole = 6.022x10²³ atoms).
Moles Au:
5.00g Au * (1mol / 196.97g) = 0.0254 moles of Au
Atoms of Au:
0.0254 moles * (6.022x10²³ atoms / 1 mole) =
1.53x10^22 atoms of AuWhat volume is occupied by 3.00 moles of nitrogen under a pressure of 202 kPa and a temperature of 323K? R = 8.314 kPa L/mol K INICI
Answer:
39.9 L
Explanation:
Use PV = nRT to solve this problem.
Substitute the values known.
P is pressure, which is 202 kPa, V is volume, which we do not know, n is moles, which is 3, R is 8.314, and T is temperature, which is 323K.
Set up your equation as follows [tex]202 kPa V = 3.00mol (\frac{8.314 kPa L }{mol K} ) 323K[/tex]
Solve for V, multiply the right side of the equation and divide by the pressure, 202 kPa.
This results in Volume being 39.9 L
The formula for calculating kinetic energy is ________
Answer:
[tex]\boxed{\bold { \large { \boxed {KE=\frac{1}{2} mv^2}}}}[/tex]
Explanation:
Kinetic energy formula
[tex]\displaystyle KE=\frac{1}{2} mv^2[/tex]
[tex]\displaystyle KE \Rightarrow \sf kinetic \ energy \ (J)[/tex]
[tex]\displaystyle m \Rightarrow \sf mass \ (kg)[/tex]
[tex]\displaystyle v \Rightarrow \sf velocity \ (m/s)[/tex]
Which of the following has the highest electronegativity?
A. N
B. P
C. O
D. Si
Answer:
O has the highest electronegativity, so option C is the answer
List the subtances in the bar chart in order of increasing melting point (lowest melting point first)
Question 12 (1 point)
The most stable isotope of hydrogen, which is very first element on the periodic table, is H-1 that has no neutrons. So, why is this atom stable?
how many molecules are in 6.9 moles of CO2?
7th grade science pls help
Answer: The last answer.
Explanation:
Please help me! I would appreciate it if you can!
Answer:
weather
cool
high pressure
low pressure
wind
humidity
more
relative humidity
condense
dewpoint
dew
frost
Explanation:
Which is not a direct classification of matter?
a. Element
b. Homogenious Mixture
c. Mixture
d. Pure Substance
Answer:
d
Explanation:
