When the enthalpy of products is higher than that of reactants, such a reaction is said to be endothermic.
EnthalpyThe enthalpy of a system refers to the heat content of the system.
When the enthalpy of reactants is higher than that of products in a reaction, such a reaction is said to be exothermic. On the other hand, if the enthalpy of products is higher than that of the reactants, it is endothermic.
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2. How many grams of NaCl are required to prepare 0.40 L of a 0.75 M solution?
The mass of a NaCl solution that is required to prepare 0.40 L of a 0.75 M solution is 17.55g. Details about mass can be found below.
How to calculate mass?The mass of a substance can be calculated by multiplying the number of moles by its molar mass.
However, the number of moles of a solution must be initially calculated by using the following formula:
molarity = no of moles ÷ volume
no of moles = 0.75 × 0.40
no of moles = 0.3 moles
mass of NaCl = 0.3 × 58.5 = 17.55g
Therefore, the mass of a NaCl solution that is required to prepare 0.40 L of a 0.75 M solution is 17.55g.
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2.
An ion has 15 protons, 16 neutrons, and 18 electrons.
a.
b.
What is the atomic number?
What is the mass number?
What is the overall charge?
d. Write the isotope notation.
C.
I have to pick which one is an oxidation reduction reaction please help!!
(You do) If you have 47.2 mol of Na available, along with an excess of Cl₂, how many grams of NaCl can you produce?
Equation: 2Na+Cl2=2NaCl
Answer:
2,760 grams NaCl
Explanation:
To find grams of NaCl, you need to (1) convert moles of Na to moles of NaCl (via mole-to-mole ratio from reaction) and (2) convert moles of NaCl to grams (via molar mass from periodic table). The final answer should have 3 significant figures based on the given measurement.
2 Na + Cl₂ --> 2 NaCl
Molar Mass (NaCl) = 22.99 g/mol + 35.45 g/mol
Molar Mass (NaCl) = 58.44 g/mol
47.2 moles Na 2 moles NaCl 58.44 grams
---------------------- x --------------------------- x ------------------------- =
2 moles Na 1 mole NaCl
= 2,758.368 grams NaCl
= 2,760 grams NaCl
At 25oc, enough distilled water is added to a 30.0 ml sample of hno3(aq) with a ph of 4.20 so that the final ph of the diluted solution is 5.20. the volume of distilled water added to the original solution is closest to
The volume of distilled water added to the original solution is closest to 300.0 ml.
What is pH?The potential of hydrogen is a measure of the acidity or alkalinity of a solution equal to the common logarithm of the reciprocal of the concentration of hydrogen ions in moles per cubic decimetre of solution.
Concentration of 30.0 ml sample of [tex]HNO_3[/tex] solution is = 6.31 X [tex]10^{-5}[/tex] M
pH of diluted [tex]HNO_3[/tex] solution = 5.20
We know that,
[tex]pH= -Log [H^+][/tex]
[tex]5.20= -Log [H^+][/tex]
[tex][H^+] = 10^{-5.2} = 6.31 X 10^{-6} M[/tex]
Hence, concentration of unknown diluted [tex]HNO_3[/tex] solution is 6.31 X [tex]10^{-5}[/tex] M.
By the use of the equation:
[tex]HNO_3[/tex] Concentration = [tex]HNO_3[/tex] diluted
[tex]V_{dil} = \frac{(C_conc X V_conc)}{(C_{dil})}[/tex]
[tex]V_{dil}[/tex] = (6.31 X [tex]10^{-5}[/tex] M X 30.0 ml) ÷ (6.31 X 10^{-6} M)
[tex]V_{dil} = 300.0 ml[/tex]
Hence, the volume of distilled water added to the original solution is closest to 300.0 ml.
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How is the modern periodic table different from Dmitri Mendeleev's table?
A. Elements that have similar properties are now grouped together.
O B. Elements are now organized by increasing atomic mass.
OC. The lanthanides and actinides are now in rows below the main
table.
D. The table is now used to predict the properties of elements.
Elements are now organized by increasing atomic mass. Hence, option B is correct.
What is a periodic table?The periodic table is a tabular array of chemical elements organized by atomic number.
Mendeleev's periodic table orders the elements based on their atomic mass whereas the Modern periodic table orders the elements based on their atomic number.
Hence, option B is correct.
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A 140.05g sample of NiSO4 . XH2O is heated until there is no further decrease in the mass. The mass of the anhydrous salt is 77.5g. What is the value of X?
From the calculations, the value of x is found to be 7.
What is the anhydrous salt?The anhydrous salt is the salt that does not contain the water of crystallization.
We know that;
Number of moles of anhydrous salt = number of moles of hydrated salt
Number of moles of anhydrous salt = 77.5g/155 g/mol = 0.5 moles
Number of moles of hydrated NiSO4= 140.05g/155 + 18x
Thus;
0.5 = 140.05g/155 + 18x
0.5 (155 + 18x) = 140.05
77.5 + 9x = 140.05
x = 140.05 - 77.5 /9
= 7
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Please hurry! classify the following as a
heterogeneous mixture,
homogeneous mixture (solution), or
a pure substance:
s'mores
a. heterogeneous mixture
b. homogeneous mixture/solution
c. pure substance
Answer:it’s A
Explanation:
Smores are made up of different materials are made by squashing a hot, oozing marshmallow with chocolate between two Graham crackers. This is heterogeneous mixture.
What are S’mores?A dessert consisting usually of toasted marshmallow and pieces of chocolate bar sandwiched between two graham crackers. Graham crackers, marshmallows, and chocolate are used to make s'mores. Homogenous mixture: A homogeneous mixture is a mixture of substances blended so thoroughly that you cannot see individual substances. Example- A mixture of salt and water, A mixture of water and sugar.
Heterogeneous mixture: A heterogeneous mixture is a mixture of two or more compounds. Example- Vegetable soup is a heterogeneous mixture. Any given spoonful of soup will contain varying amounts of the different vegetables.
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What is the general formula for a straight-chain alkane?
C2H8
CH3CH3CH3
CH3CH2CH3
CH3CH2CH2CH3
Answer:
The general formula for a straight chain alkane is CnH(2n+...so correct option is C and D
why does the sloth have both a scientific name and common name
PLEASE HURRY!
Determine if the following two structures are identical, isomers, or unrelated?
Based on the given information, the given structures are isomers, i.e., option B as they have different arrangements, but the same molecular formula.
What are isomers?Isomers are organic compounds having the same molecular formula and different molecular structures.
This difference is due to varying spatial arrangement of atoms in the compounds.
Isomers of different compounds have different properties based on the molecular formula.
Thus, the correct option is B.
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What best describes the relationship between photosynthesis and cellular respiration? a.Celluar respiration and photosynthesis are identical reactions. b. photosynthesis is just like celluar respiration, but oxygen is involved. c. celluar respiration and photosynthesis are not related at all. d. photosynthesis and celluar respiration are opposite reactions.
The statement 'photosynthesis and cellular respiration are opposite reactions' best describes the relationship between photosynthesis and cellular respiration.
What is cellular respiration?Cellular respiration is a chemical process where foods and oxygen are used to generate ATP in aerobic conditions.
Conversely, photosynthesis is a chemical process where light and carbon dioxide are used to generate chemical energy.
In conclusion, the statement 'photosynthesis and cellular respiration are opposite reactions' best describes the relationship between photosynthesis and cellular respiration.
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What is a renewable resources
Answer: A renewable resource is a resource that can easily be replaced over a short amount of time.
Explanation: Unlike the non-renewable resources, they can be replenished.
Examples for non-renewable: coal, oil, and fossil fuels.
Examples for renewable resources: Wind, nuclear, solar power, and water.
What is true about the breakdown of starch?
a.
Animals, but not plants, can break down starch.
b.
Organisms break down starch into carbon, hydrogen, and oxygen atoms.
C. Organisms break down starch into carbohydrate subunits.
d.
Starch breakdown is not a chemical reaction
Answer:
Option C
Explanation:
Organisms break down starch into glucose
Which is a carbohydrate subunitThe organisms are found in our digestive system helps in break down of starch and turns them into glucoseAnswer:
Organisms break down starch into carbohydrate subunits.
Explanation:
Starch is a necessary amount of our bodyIt is used as an carbohydrate subunit well known as glucoseIt is converted through organismsSo option C is correct
This diagram models a sound wave from a car horn hitting a wall. According to the model, which statement best describes what happens to the sound energy when the sound wave hits the wall?
Answer:
When sound wave hits the wall , some portion of the sound is reflected back to air which is converted into heat energy and
lost in the atmosphere and some of its transmitted through the walls.
Why is water used as a solvent in many solutions?
A Water dissolves other water molecules.
B Water dissolves any chemical.
C Water dissolves nonpar molecules.
D Water dissolves polar molecules.
O A
OB
O C
O D
Mary has a sample of permanganate (MnO4-1), in which Manganese has an oxidation state of +7. She wants to reduce the Manganese, which means she needs a substance that will oxidize readily. Which of the following substances should she choose? Explain your reasoning.
Lithium solid (Li)
Silicon solid (Si)
Bromine liquid (Br2)
plain how to calculate the number of atoms in 31.1 g of Au.
Answer:
See Below
Explanation:
mole weight of Au ( gold) = 196.97 gm
31.1 / 196.97 = number of moles of Au
Number of moles * Avagadro's Number = number of atoms
31.1 / 196.97 * 6.022 x 10^23 = 9.508 x 10^22 atoms
What is the mass in grams of each of the following?
a.) 6.02 x 1024 atoms Bi
c.) 6.02 x 1022 atoms He
e.) 6.02 x 10¹5 atoms U
b.) 1.00 x 1024 atoms Mn
d.) 6.02 x 10¹5 atoms N
Answer:
a. 208g Bi
c. 0.0400g He
e. 2.38g U
b. 9.12g Mn
d. 1.40g N
Explanation:
I apologize in advance if any are incorrect. Hopefully this helps.
Suppose cobalt-60 undergoes a type of radioactive decay that does not
change the identity of the isotope. which type of decay did the isotope
undergo?
a. delta
b. gamma
c. alpha
d. beta
what is indicated by the methyl- prefix
Answer:
B
Explanation:
The methyl prefix means theres a CH3 group bonded to a carbon in a hydrocarbon. This is called branching because it looks like a branched tree. This is literally cheating but you do you.
Which two phase changes occur when you increase the heat?
Answer:
Heat going into a substance changes it from a solid to a liquid or a liquid to a gas. Removing heat from a substance changes a gas to a liquid or a liquid to a solid.
Liquid → Gas:
VaporizationGas → Liquid:
CondensationSolid → Liquid:
Melting or fusion
Solid → Gas: Sublimation
Explanation:
what is the colour of our oxygen
best answer will get 30 points
Answer:
colourless
Explanation:
although the gaseous form of oxygen is colourless
when it liquefies it turns into a blue fluid.
hope this helps:)
An isotope with a half life of 10 min and a starting sample size of 100 g would have
how many grams remaining after 30 minutes?
Answer:
12.5 gm left
Explanation:
30 minutes is THREE half lives
1/2^3 = 1/8th would be left
100g * 1/8 = 12.5 gm
Due to the fact that the half-life of the isotope is just 10 minutes, there will be 12.5 grammes of the original sample, which weighed 100 grammes, left after 30 minutes.
We can use the half-life to figure out how much of the isotope is left after 30 minutes by looking at how it breaks down.
A radioactive isotope's half-life is the amount of time it takes for half of the original sample to decay. In this case, 10 minutes is the half-life.
After 10 minutes, 50 g of the isotope will be left from the 100 g sample because 50 g of it will have decayed. Now, the first half-life has come to an end.
After another 10 minutes (for a total of 20 minutes), half of the leftover 50 g will decay, leaving us with 25 g of the isotope.
After another 10 minutes, for a total of 30 minutes, half of the 25 g that is still there will decay, leaving us with 12.5 g of the isotope.
So, there will be 12.5 grammes of the isotope left from the 100 g sample after 30 minutes.
It's important to keep in mind that the process of decay is exponential. With each passing half-life, the amount of isotope that is left drops by half. Because of this, it takes longer and longer for the amount of isotope that is left to decrease significantly, but it will never hit zero.
Understanding the idea of "half-life" is important in many areas of science, such as atomic dating, nuclear medicine, and environmental science, because it helps figure out how fast radioactive materials break down and what effects they might have on living things and the environment.
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Which radioisotope is used to treat thyroid disorders?.
Answer:
I-123 and I-131
Explanation:
Radioactive iodine takes advantage of the fact that thyroid cells and thyroid cancer cells absorb iodine; therefore, it has been used to diagnose or treat various thyroid disorders. Iodine is made into two radioactive isotopes, I-123 and I-131, that are commonly used in patients with thyroid disease.
Why the bond angle of ammonium is larger than water?
Answer:
This repulsion is stronger than the repulsion between the lone pair and the three bond pairs on the nitrogen atom. Since the repulsions on the bond pairs in H2O molecule are greater than that in NH3 the bond angle in water is less than that of ammonia.
Provide the bond type, molecular structure, and intermolecular forces for h2o and co2. compare and contrast these structures from nacl. using that information, explain why each of these are in a different phase at room temperature.
Intermolecular forces are the forces present between the molecules. In carbon dioxide the intermolecular force is LDM and in water, hydrogen, LDM, and dipole-dipole are present.
What is molecular structure?Molecular structures are the arrangement of the atoms in the three-dimensional phase of the molecule along with their electrons. Water has a bent shape while carbon dioxide has linear shape geometry.
Water is a polar covalent molecule that has hydrogen and dipole-dipole bonding and forces that makes them strong enough to make them liquid at RT. On another hand carbon dioxide is a nonpolar covalent molecule that is gas at room temperature.
Sodium chloride is an ionic compound that has anions and cations in it. As it has high lattice energy it remains solid at room temperature.
Therefore, water, carbon dioxide, and sodium chloride are at different phases at room temperature.
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how do gases exert pressure into a cylindrical container
Answer: The molecules are continually colliding with each other and with the walls of the container. When a molecule collides with the wall, they exert small force on the wall The pressure exerted by the gas is due to the sum of all these collision forces. The more particles that hit the walls, the higher the pressure. If a gas is heated up, its particles move around more quickly. They hit the walls of their container harder and more often. This increases the pressure. Sometimes the pressure gets so great that the container bursts.
Explanation:
Answer:
When a molecule collides with the wall, they exert small force on the wall The pressure exerted by the gas is due to the sum of all these collision forces.
Explanation:
The molecules are continually colliding with each other and with the walls of the container. When a molecule collides with the wall, they exert small force on the wall The pressure exerted by the gas is due to the sum of all these collision forces. The more particles that hit the walls, the higher the pressure.
Toothpaste contains Sodium fluoride which is used to prevent tooth decay. How many grams are in 1 mole NaF?
The answer is 42 grams of NaF are there in 1 mole.
What is a mole ?A mole is defined as 6.022 × 10²³ atoms, molecules, ions, or other chemical units.
and the molar mass of a substance is defined as the mass of 1 mole of that substance, expressed in grams per mole.
It is equal to the mass of 6.022 × 10²³ atoms, molecules, or formula units of that substance.
Molar Mass , i.e. mass of 1 mole of NaF is sum of molar mass of Na and F
23 + 19
42 grams
Therefore 42 grams of NaF Sodium-fluoride are there in 1 mole.
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under what circumstances will a scientific theory be changed or dicarded
Answer:
I think it's..
Explanation:
You can explain more, please.