Select all that apply.

When the products of a reaction have a higher enthalpy than the reactants:

The change in enthalpy is positive.
The reaction is exothermic.
The reaction is endothermic.
The change in enthalpy is negative.

Answer:

Option C

Explanation:

Organisms break down starch into glucose

Answer:

Organisms break down starch into carbohydrate subunits.

Explanation:

So option C is correct

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.

Elements are now organized by increasing atomic mass. Hence, option B is correct.

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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Based on the given information, the given structures are isomers, i.e., option B as they have different arrangements, but the same molecular formula.

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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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

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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The statement 'photosynthesis and cellular respiration are opposite reactions' best describes the relationship between photosynthesis and 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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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.

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.

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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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.

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.

Answer:

I think it's..

Explanation:

You can explain more, please.

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.

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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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:

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

Answer:

The general formula for a straight chain alkane is CnH(2n+...so correct option is C and D

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.

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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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.

The volume of distilled water added to the original solution is closest to 300.0 ml.

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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The answer is 42 grams of NaF are there in 1 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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From the calculations, the value of x is found to be 7.

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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Answer:

colourless

Explanation:

although the gaseous form of oxygen is colourless

when it liquefies it turns into a blue fluid.

hope this helps:)

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.

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.