Answer:
I don't understand the question
Explanation:
what is your name
The half-life for a 400-gram sample of radioactive element X is 3 days. How much of element X remains after 15 days have passed?
A.
12.5 g
B.
25 g
C.
50 g
D.
100 g
Answer:
The correct answer is - A. 12.5 gram.
Explanation:
Given:
The initial amount of sample = 400 gram
the half-life cycle = 3 days
after 15 days remain value = ?
Solution:
The number of half-lives in 15 days = 15/3
= 5 half-lives
the remaining amount of sample after one half-life 3 days = 400/2 = 200
the remaining amount of sample after 2nd half-life or 6 days= 200/2 = 100
the remaining amount of sample after 3rd half-life or 9 days= 100/2 = 50
the remaining amount of sample after 4th half-life or 12 days= 50/2 = 25
the remaining amount of sample after 5th half-life or 15 days= 25/2 = 12.5 gram
Thus, the correct answer is = 12.5 g.
A sample of polonium-210 has an initial mass of 390 milligrams (mg). If the half-life of polonium-210 is 36 days, how many mg of the sample remains after 72 days?
A.
392 mg
B.
195 mg
C.
97.5 mg
D.
48.75 mg
Answer: D. 48.75
Explanation: just took the test
Answer:
D
Explanation:
I got this question right on my test.
How many moles are in 9.83 x 1021 atoms of Na
Answer:
0.016 molesExplanation:
To find the number of moles in a substance given it's number of entities we use the formula
[tex]n = \frac{N}{L} \\[/tex]
where n is the number of moles
N is the number of entities
L is the Avogadro's constant which is
6.02 × 10²³ entities
We have
[tex]n = \frac{9.83 \times {10}^{21} }{6.02 \times {10}^{23} } \\ = 0.01632...[/tex]
We have the final answer as
0.016 molesHope this helps you
Which of the two Lewis/electron dot structure representations, which is
the correct one for oxygen gas? PICTURE BELOW
Answer:
A
Explanation:
What is the name for the compound with a chemical formula B6Si.
The chemical formula B₆Si belongs to the compound silicon hexaboride.
_____ is the process of linking smaller molecules to form long chains of higher molecular weight.
[H3O+] = 2.9 x 10-10 M
ph level
Answer:
9.54
Explanation:
Fr the question given above, the following data were:
Concentration of hydronium ion [H3O⁺] = 2.9x10¯¹⁰ M
pH =?
The pH of the solution can be obtained as follow:
pH = –Log [H3O⁺]
pH = –Log 2.9x10¯¹⁰
pH = 9.54
Thus, the pH level of the solution is 9.54
Which statement best explains the genetic variation that results from sexual
reproduction?
A. Each chromosome contains many different genes.
B. Offspring receive a mix of genes from two different parents.
c. Offspring receive genes that are exactly the same as one parent's
genes.
O D. Each chromosome contains many copies of the same gene.
Answer:
Each chromosome contains many copies of the same gene
Answer:
Offspring receive a mix of genes from two different parents
Good luck!
A___
is a
small, rocky object
that orbits the sun
and has broken
off from a comet
or asteroid.
(Fill in the blank)
Answer:
I think it is a rock...
Explanation:
maybe idrk tho
What is the difference between how a mercury barometer and an aneroid barometer measure air pressure?
Answer:
Aneroid barometer and mercury barometer are such two types. The main difference between aneroid and mercury barometer is that aneroid barometer measures the atmospheric pressure using the expansion of a metal whereas mercury barometer measures the atmospheric pressure by adjusting the height of mercury inside a tube.
Explanation:
How does nitrogen in the atmosphere become beneficial to plants and eventually animals?
O Nitrogen must be mixed in the soil by earthworms,
O Nitrogen must be converted into a useful form by bacteria,
O Nitrogen must come in contact with decaying organic material,
O Nitrogen must come in contact with the ground through rainfall
Answer:
O Nitrogen must be converted into a useful form by bacteria.
This bacteria is called the nitrogen fixing bacteria such as the Rhizobium bacteria.
2 Which of the gases in air are elements? Explain how you can tell.
Answer:
I'll explain.
Explanation:
The molecules of two different elements, nitrogen and oxygen, make up about 99 percent of the air. The rest includes small amounts of argon and carbon dioxide. Oxygen is the life-giving element in the air. You can tell because they're on the periodic table which is a table for elements.
Explanation:
nitrogen and oxygen are the gases in the air which are elements you can simply say it by looking the periodic table
131.39 g/mol C2HCl3
find the molecular formulas
Answer:
Find the mass of 1 mole.
mass of
1
mole of
131.39
g
m
o
l
C
2
H
C
I
⋅
3
=
37.04000067
g
Explanation:
hope it helps make brainlliest ty
Which of the following is a characteristic shared by all living things?
A. They have tissues and organs,
B. They take in oxygen.
C. They make more individuals of the same kind.
D. They move.
Determine the number of electrons in an Cl ion with a charge of -3
Answer:
There are 20 electrons.
Explanation:
Chlorine has 17 electrons in its atom to begin with (you can tell from the proton number in the periodic table).
A charge of -3 means that the chlorine atom gained 3 electrons, and now needs to lose 3 electrons to return to its atom configuration.
What is the pOH for a solution whose pH is 2?
Answer:
12
Explanation:
Because it is pH and pOH, you can use the relationship of 14-pH=pOH, or 14-pOH=pH. Using this you should get the pOH to be 12.
Consider the oxidation of sodium metal to sodium oxide described by the balanced equation:
4 Na + O2 → 2 Na2O. What is the theoretical yield of Na2O in grams from 9.0 mol of O2?
show steps
Answer:
1116 g.
Explanation:
The balanced equation for the reaction is given below:
4Na + O₂ —> 2Na₂O
From the balanced equation above,
1 mole of O₂ reacted to produce 2 moles of Na₂O.
Next, we shall determine the theoretical yield of Na₂O. This can be obtained as follow:
From the balanced equation above,
1 mole of O₂ reacted to produce 2 moles of Na₂O.
Therefore, 9 moles of O₂ will react to produce = 9 × 2 = 18 moles of Na₂O.
Finally, we shall determine the mass in 18 moles of Na₂O. This can be obtained as follow:
Mole of Na₂O = 18 moles
Molar mass of Na₂O = (23×2) + 16
= 46 + 16
= 62 g/mol
Mass of Na₂O =?
Mass = mole × molar mass
Mass of Na₂O = 18 × 62
Mass of Na₂O = 1116 g
Thus, the theoretical yield of Na₂O is 1116 g.
In a reaction, the actual yield is always at least as large as the theoretical yield.
True or false.
give short explanation on answer
what is the chemical equation for aq nitrate ion reacts with s arsenic trihydride and produces s arsenic and g ammonia?
Answer:
Explanation:
What is the empirical formula for a compound if a 2.50g sample contains 0.900g of calcium and 1.60g
of chlorine? (3pts]
Answer:
CaCl₂
Explanation:
First we convert the given masses of elements into moles, using their respective molar masses:
0.900 g Ca ÷ 40 g/mol = 0.0225 mol Ca1.60 g Cl ÷ 35.45 g/mol = 0.045 mol ClNow we divide those numbers of moles by the lowest value among them:
0.0225 mol Ca / 0.0225 mol = 10.045 mol Cl / 0.0225 mol = 2Meaning the empirical formula for the compound is CaCl₂.
Name the part in red:
H2 + O2 -> H2O
Answer:subscript
Explanation:
Select the correct answer.
What quantity might be measured in units of kilograms?
A.
the brightness of a candle
B.
the volume of a bottle
C.
the mass of a marble
D.
the electric current in a wire
Answer:
The mass of a marble.
Explanation:
Units of the other answers:
A: Light - Lumen (lm)
B: Volume - cm^3
D: Electric current - Ampere
Becky wants to model an ecosystem. Which of the following modeling tools would best help her illustrate an ecosystem?
A.
a rubber ball
B.
a terrarium
C.
a map
D.
a set of building blocks
Answer:
c
Explanation:
You tested the rocket with three mixtures of fuel having different masses of oxygen
and hydrogen. What is the relationship between the masses of oxygen and hydrogen in
each of the tests?
Answer:
As the oxygen is only transferred from the copper oxide to form water inside the apparatus, any gain in mass is due to hydrogen combined with the oxygen to form water. The ratio of the two masses enables the mass of oxygen combining with 1 g of hydrogen to be calculated.
Hydrogen and oxygen are the elements used as fuels in rockets as they are propellants. In each of the tests, the ratio of the mass of hydrogen to oxygen is 1:8.
What is the combustion of rocket fuel?Combustion has been the chemical reaction that involves reactants combining and reacting with oxygen resulting in heat and light formation. They are majorly used in propelling engines and in rocket fuels.
In a rocket engine oxygen acts as the oxidizer that reacts with hydrogen atoms to derive the heat and energy so that the engine can move and produce thrust. It uses Newton's third law to create energy and accelerate upwards.
The mixtures of fuel contain various masses that are present in a ratio of 1:8 (hydrogen: oxygen) as masses of hydrogen are 1, 2, and 5 mg, whereas oxygen is 8, 16, and 40 mg. It can be concluded that 1 part of hydrogen reacts with 8 parts of oxygen in the rocket fuel mixture.
Therefore, the rocket fuel mixtures contain a 1:8 ratio of the masses of hydrogen: oxygen that undergoes combustion reaction.
Learn more about combustion, here:
https://brainly.com/question/14335621
#SPJ2
ii) Sodium thiosulphate dissolves in dilute nitric acid at a steady rate. Copy out which
of the following changes would quicken up the reaction- 3
a. Cooling the reacting vessel to drop the temperature.
b. Breaking the reactants into smaller pieces.
c. Adding more concentrated acid.
d. Using more sodium thiosulphate.
Answer:
d
Explanation:
At a pressure of 1 atm, the temperature 115.9 K is called the fill in the blank 1 of Kr . The normal boiling point for Kr is at K The triple point pressure for Kr is atm The critical pressure for Kr is 54.3 atm. At temperatures above 209.4 K and pressures above 54.3 atm, Kr is a _________ . Kr is a _________ at 50.3 atm and 105 K. Kr is a _________ at 0.720 atm and 131 K. Kr is a _________ at 1.00 atm and 118 K.
Answer:
melting point, 119.8 K, 0.72 atm, supercritical fluid, solid, gas, liquid.
Explanation:
Let's refer to the phase diagram (not to scale) for krypton.
At a pressure of 1 atm, the temperature 115.9 K is called the melting point of Kr, and it is the temperature at which it passes from solid to liquid.
The normal boiling point for Kr is at 119.8 K, which is, at 1 atm, the limit between the liquid and the gas state.
The triple point pressure for Kr is 0.72 atm, as can be seen in point C.
The critical pressure for Kr is 54.3 atm.
At temperatures above 209.4 K and pressures above 54.3 atm, Kr is a supercritical fluid, according to the region it is in the phase diagram.
Kr is a solid at 50.3 atm and 105 K, according to the region it is in the phase diagram.
Kr is a gas at 0.720 atm and 131 K, according to the region it is in the phase diagram.
Kr is a liquid at 1.00 atm and 118 K, according to the region it is in the phase diagram.
The number of atoms in a 158.4 g sample of CO2 gas at STP is:
1.277 x 1025 atoms
2.167 x 1024 atoms
6.502 x 1024 atoms
6.651 x 1024 atoms
Answer:
Option B, 2.167 x 1024 atoms
Explanation:
1 mole of CO2 = 44.01 grams
Number of moles of CO2 in 158.4 gram sample
[tex]\frac{158.4}{44.01} \\3.95[/tex]moles
Number of atoms in one mole is [tex]6.02*10^{23}[/tex]
Number of atoms in 3.95 moles [tex]2.167 *10^{24}[/tex]
Hence, option B is correct
I need the correct answers
Answer:
Acids: Tastes Sour
Has a ph less than 7
Base: Bitter
Has a ph greater than 7
slippery
Acid&Base: Conducts electricity
Write out and balance the chemical equation:
A solution of nickel (II) chloride reacts with a solution of potassium hydroxide
to produce solid nickel (II) hydroxide and a solution of potassium chloride.
Explanation:
NiCl2 + KOH = NiOH + KCl
since nickel is the primary element in nickel ii chloride, find the oxidation no of nickel in the compound and chlorine should have 2 as a subscription since the ii in the compound represents that nickel has an oxidation no of 2
Please someone answer this asap
Answer:
b or c but I would just pick c
Answer:
C
Explanation:
Sun is an energy source not a matter.