The isotope sodium-24 has a half-life of 15 hours. Starting with 22 grams, how much remains in 45 hours
The amount, in grams, that will remain of the isotope will be 2.75 grams
Half-lifeIt is the time it takes for a given amount of radioactive substance to decay into half of its original amount.
The half-life is 15 hours. This means that the amount is halved every 15 hours.
If the starting amount is 22 grams, it will become 11 grams (22/2) after the first 15 hours. The 11 grams will become 5.5 grams (11/2) after another 15 hours, making 30 hours.
The 55.5 grams remaining will become 2.75 grams (5.5/2) if another 15 hours should pass, making a total of 45 hours that have passed.
Thus, only 2.75 grams of the isotope will remain in 45 hours.
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Unit 8 Multiple Choice Questions
1. Which statements regarding the presence of greenhouse gases in the
atmosphere is a FALSE statement?
4
OA. The atmosphere is mostly non-greenhouse gases
OB. The atmosphere contains a small amount of greenhouse gases
C. The atmosphere has never changed
O
D. The greenhouse gases in the atmosphere have a large impact on the Earth's
climate.
This is a required question
Answer:
C
Explanation:
just did it
A catalyst ______. (select all that apply.) multiple select question. is depleted in a chemical reaction undergoes no permanent change during a reaction does not participate in a chemical reaction
The statements that are true regarding a catalyst are as follows:
It undergoes no permanent change during a reaction
It does not participate in a chemical reaction
What is a catalyst?
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.
A catalyst increases the rate at which a chemical reaction occurs by decreasing the activation energy of the reaction.
Since a catalyst is not used up in the reaction, the following statement applies:
It undergoes no permanent change during a reaction
It does not participate in a chemical reaction
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Which compound releases hydroxide ions in an aqueous solution.
The compound that releases hydroxide ions in an aqueous solution would be a base.
What are bases?Bases are substances that when ionized in water, produce hydroxide ions as the only negative ion.
Bases are as opposed to acids. The latter produces hydrogen ions as the only positive ion when ionized in water. For example, sodium hydroxide ionizes in aqueous solutions as follows:
[tex]NaOH --- > Na^+ + OH^-[/tex]
Bases can also be defined as substances whose pH is above 7.
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What causes lines in a line spectrum?
A. Transitions that don't happen to an electron
B. Wavelengths of absorbed or emitted photons
C. Quantum numbers associated with an electron
D. Edges on the prism used to separate wavelengths
Wavelengths of absorbed or emitted photons causes lines in a line spectrum.
What causes lines in a line spectrum?Spectral lines are produced by transitions of electrons within atoms. As the electrons move closer or farther from the nucleus of an atom, energy is released in the form of light is emitted.
So we can conclude that Wavelengths of absorbed or emitted photons causes lines in a line spectrum.
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Identify a cation. An atom that has gained a proton. An atom that has lost an electron. An atom that has gained an electron. An atom that has lost a proton.
the answer would be B an atom that has lost an electron
If 23.0 g of Na react completely with 35.5 g of Cl2 to form 58.5 g of NaCl, what mass of Cl2 is required to react completely with 10.0 g of Na
The mass of Cl₂ required to react completely with 10.0 g of Na given the data is 15.4 g
Balanced equationNa + ½Cl₂ —> NaCl
From the balanced equation above,
23 g of Na required 35.5 g of Cl₂
How to determine the mass of Cl₂ requiredFrom the balanced equation above,
23 g of Na required 35.5 g of Cl₂
Therefore,
10 g of Na will require = (10 × 35.5) / 23 = 15.4 g of Cl₂
Thus, 15.4 g of Cl₂ are required for the reaction
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Match the following
1. coefficient
2. law of conservation of mass
3. product
4. reactant
the number written in front of a
chemical symbol in an equation
principle that during a chemical
reaction the total mass of the system is
unchanged
the substance made in a chemical
reaction
the starting material in a chemical
reaction
The order would be coefficient, law of conservation of mass, products, and reactants respectively.
Word matchingThe number written in front of a chemical symbol in an equation is called a coefficient.
The total mass of a system being unchanged is known as the law of conservation of mass
The substances made in chemical reactions are called products.
The starting materials in chemical reactions are called reactants.
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A solvent is added to dissolve only one mixture component and then the liquids are separated. Choose... A liquid is carefully poured out, leaving the solid behind in the container. Choose... A solid is caught on paper or a membrane while the liquid passes through. Choose... A solid mixture is heated. One component transitions directly between solid and gas. Choose...
The solid would be caught on a filter paper or membrane while the liquid passes through.
FiltrationFiltration is used to separate a mixture of insoluble substances in a liquid.
Since the aim is to separate the insoluble component of the mixture from the liquid, filtration using a suitable filter paper or membrane will be the way out.
The liquid will pass through the filter paper or the membrane while the insoluble component will be caught. This can then be dried and collected accordingly.
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Identify the products of the reaction between 2KOH and H₂SO4- OH.
Answer:
The reaction is H2SO4 + 2KOH = K2SO4 + 2H2O
It resembles a double displacement reaction.
Notice how it is balanced so that there are the same number of each type of atom on both sides of the reaction.
The potassium sulfate will ionize into K+ ions and SO4-- ions, but the formula is usually written as above.
Based on the shapes of the water drops in part D, how does the attractive force between water and wax compare to the attractive force between water and glass?
Answer:
Because the cohesive forces inside the droplets are stronger than the adhesive forces between both the drops and the wax, water does not penetrate waxed surfaces. Because the adhesive forces between the liquid and the glass are stronger than the cohesive forces inside the water, water wets glass and spreads out across it.
Explanation:
EDMENTUM
What is the Noble-gas notation for sodium?
O [Ar]3s¹ 1
O [He]2s²2p 3s¹
[Ne]3s²3p4
O[Ne]3s¹
Answer:
The noble gas notation for sodium is [Ne] [tex]3s^{1\\[/tex]
Explanation:
Which scientist determined the charge of the electron?.
Answer:
J.J. Thomson
Explanation:
A sample of cobalt has a mass of 27 g and a density of 9 g/cm^3. What would be its volume?
Measurements show that unknown x compound has the following composition:
carbon 18.1%
hydrogen 2.27%
chlorine 79.8%
Write the empirical chemical formula of x.
The empirical formula of the compound with the percent composition C 18.1%, H 2.27%, Cl 79.8% is C₂H₃Cl₃.
What is an empirical formula?It is the minimum ratio between the elements that form a compound.
Step 1: Divide each percentage by the molar mass of the element.C: 18.1/12.01 = 1.51
H: 2.27/1.01 = 2.25
Cl: 79.8/35.45 = 2.25
Step 2: Divide all the numbers by the smallest one.C; 1.51/1.51 = 1
H: 2.25/1.51 ≈ 1.5
Cl: 2.25/1.51 ≈ 1.5
Step 3: Multiply all the numbers by 2 so all of them are whole.C: 1 × 2 = 2
H: 1.5 × 2 = 3
Cl: 1.5 × 2 = 3
The empirical formula is C₂H₃Cl₃.
The empirical formula of the compound with the percent composition C 18.1%, H 2.27%, Cl 79.8% is C₂H₃Cl₃.
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1CO₂ (g) + 1C (s) → 2CO (g)
Keq =
Answer:
the equation is balanced
Determine the empirical formula of a compound containing 40. 6 grams of carbon, 5. 1 grams of hydrogen, and 54. 2 grams of oxygen.
in an experiment, the molar mass of the compound was determined to be 118. 084 g/mol. what is the molecular formula of the compound?
for both questions, show your work or explain how you determined the formulas by giving specific values used in calculations
The empirical formula is C₂H₃O₂
What is Empirical formula of a compound ?The empirical formula is the simplest whole number ratio of elements present in a compound.
The total molar mass of the compound is 118.084 g/mol.
mass of Carbon present = 40.6
mass of Hydrogen present = 5.1 grams
mass of Oxygen present = 2 grams
Moles of C = 40.6/12 = 3.38
Moles of H = 5.1/1.008 = 5
Moles of Oxygen = 54.2/15.999 = 3.38
Ratio of Moles of C to Oxygen is 1 : 1
Ratio of Moles of C to H is 1/1.5
Multiplying each mole fraction by 2
The empirical formula is C₂H₃O₂
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Calculate the concentration in gdm3 of 0.85M Ammonium Carbonate solution. [C=12, N=14, H=1, N=14, 0=16]
Answer:
You need to provide a volume for the problem to be solved.
Explanation:
What happens when less energy is entering than exiting?
Answer:
If there is a decrease in the amount of carbon dioxide or methane, the amount of energy leaving the Earth system increases, so less energy enters than exits. When less energy enters than exits, Earth's surface absorbs less energy.
Explanation:
Which description best describes volume? *
O How hard the particles are pushing on something
O How many particles of something there is
O How hot/cold something is
How much space something takes up
O8.3145 L kPa / K mol
Answer:
how many particles are pushing something
When European demand for a certain solvent declined, Dow Chemical instructed its German plant to switch to manufacturing a chemical that had been imported from Louisiana and Texas. Dow Chemical would be best described as a(n)
Dow Chemical would be best described as a multinational corporation in this scenario.
What is a Multinational corporation?
This is the type of corporation which are involved in controlling production of goods and services in at least one country different from that of residence.
Dow chemical is known to have a plant in Germany and Russia thereby making it a multinational corporation.
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how to make crystals of sodium chloride without putting sodium into hydrochloric acid
Answer:
• Reacting aqueous Sodium hydroxide solution with Magnesium chloride.
Explanation:
[tex]{ \rm{2NaOH _{(aq)} + MgCl _{2(s)} \: \dashrightarrow \: 2NaCl _{(s)} + Mg(OH)_{2(aq)} }}[/tex]
Answer:
Sodium hydroxide solution + Magnesium chloride = sodium chloride crystals
Explanation:
What is the difference between, Flame tests and Flame emission spectroscopy?
Answer:
Flame testing is an analytical technique where a sample is applied to a flame, and the characteristic emission spectrum is used to identify different elements.
Answer:
Flame testing is an analytical technique where a sample is applied to a flame, and the characteristic emission spectrum is used to identify different elements. When this technique is used to identify metal species, it is called metal flame emission testing while Flame emission spectrophotometry is based on the characteristic emission of light by atoms of many metallic elements when given sufficient energy, such as that supplied by a hot flame.
2H2O + 3HCl ——> 5H2O + Cl
how many moles of H2O are needed to make 3 moles of HCl?
Answer: 2 moles
Explanation:
We know from the equation that for every 3 moles of HCl consumed, 2 moles of water are consumed (based on the coefficients)
So, the answer is 2 moles.
The difference in the heights of the Hg columns in Diagram B is17 mm-Hg. If the atmospheric pressure is 769 mm-Hg, what is the pressure of the confined gas in mm-Hg
The pressure of the confined gas will be 769-17 = 752 mmHg
What is Manometer ?Manometer is a U shaped instrument which is used to measure the pressure acting on a column of fluid , a difference in the pressure in the two arms of the manometer causes the liquid to reach different heights.
The difference in the heights of the Hg columns in Diagram B is17 mm-Hg.
the atmospheric pressure is 769 mm-Hg,
the pressure of the confined gas in mm-Hg = ?
The pressure of the confined gas will be 769-17 = 752 mmHg
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What is the total molar concentration of ions of 1.250 0f ch30h
If someone asked you to mix up a bag of ringers solution with 150 meq/l of na , 10 meq/l of k , 8 meq/l of ca2 , and 197 meq/l of mg2-, how many grams of mg2- would you add to the mixture?
The normality is the ratio of the equivalent to the volume of the solvent. To the mixture, 1.182 gms of magnesium should be added.
What is Normality?Normality (N) is the grams or moles of solute per liter of solution.
Magnesium has 2 valence electrons in the outermost shell so,
1 mEq of Mg⁻² ions = atomic number of Mg ÷ valence electron
= 12 ÷ 2
= 6 mg
In a liter solution having 197 meq/l of Mg⁻²:
197 meq/l of Mg⁻² × 6 = 1182 mg
Therefore, 1.182 gms of magnesium ions should be added to the mixture.
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I WILL GIVE BRAINLIEST! PLEASE HELP :')
What is the volume of a gas if 0.182 moles of the gas is at 1.99 atm and 83.4oC?
Answer:
2,67 L
Explanation:
Match the following items.
1. not affected by a magnet
2. mostly space
3. flows freely but particles still attract
4. positively charged particles
5. free to move in all space
6. negatively charged particles
7. atoms nearly fixed in space
8. helium nucleus
proton
solid
liquid
gamma ray
gas
atoms
electron (beta)
alpha particles
Answer:
1. not affected by a magnet 1 liquid
2. mostly space 2 solid
3. flows freely but particles still attract 3 proton
4. positively charged particles 4 gas
5. free to move in all space 5 alpha particles
6. negatively charged particles 6 atoms
7. atoms nearly fixed in space 7 gamma ray 8. helium nucleus 8 electron (beta)
What is the ph of 0.05l of hand soap? is it acidic or basic?