What is true about endothermic reactions?

Endothermic reactions release heat to the surroundings.
The enthalpy of products in endothermic reactions is lower than the enthalpy of reactants.
The enthalpy of an endothermic reaction is positive.
Endothermic reactions have an enthalpy of zero.

Answer:

Molecule is the general term used to describe any atoms that are connected by chemical bonds. Every combination of atoms is a molecule. A compound is a molecule made of atoms from different elements. All compounds are molecules, but not all molecules are compounds.

Explanation:

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Answer:

C. Nervous

Explanation:

The nervous system is a system of the body of living organisms which includes the brain, spinal cord and nerves.

Answer:

25.8 L

Explanation:

Step 1: Write the balanced equation for the complete combustion of acetylene

C₂H₂ + 2.5 O₂ ⇒ 2 CO₂ + H₂O

Step 2: Calculate the moles corresponding to 15.0 g of C₂H₂

The molar mass of C₂H₂ is 26.04 g/mol.

15.0 g × 1 mol/26.04 g = 0.576 mol

Step 3: Calculate the moles of CO₂ produced from 0.576 moles of C₂H₂

The molar ratio of C₂H₂ to CO₂ is 1:2. The moles of CO₂ produced are 2/1 × 0.576 mol = 1.15 mol.

Step 4: Calculate the volume corresponding to 1.15 moles of CO₂

At standard temperature and pressure, 1 mole of CO₂ occupies 22.4 L.

1.15 mol × 22.4 L/1 mol = 25.8 L

Answer:

5 L

Explanation:

Molarity = mol/L   ---->    L = mol/molarity

2.0 moles / 0.4 M HF = 5 L

Answer: It does not react with water, but reacts with most acids. It combines with oxygen at room temperature to form chromium oxide. Chromium oxide forms a thin layer on the surface of the metal, protecting it from further corrosion (rusting).

Explanation:

Answer:

94.196 grams

Explanation:

Answer:

94.196 grams

Explanation:

Answer:

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Answer:

[tex]4118\ g[/tex]

Explanation:

[tex]We\ are\ given,\\No.\ of\ moles\ of\ Na_2SO_4\ provided=29\ moles\\Hence,\\Now,\\Lets\ calculate\ the\ Gram\ Molecular\ Mass\ of\ Na_2SO_4.\\We\ know\ that,\\Gram\ Atomic\ Mass\ of\ Sodium(Na) \approx 23\ g\\Gram\ Atomic\ Mass\ of\ Sulphur(S) \approx 32\ g\\Gram\ Atomic\ Mass\ of\ Oxygen(O) \approx 16\ g\\Hence,\\We\ observe\ that,\\One\ molecule\ of\ Na_2SO_4\ is\ made\ up\ of\ 2\ Sodium\ Atoms,\ 1\\ Sulphur\ Atom\ and\ 4\ Oxygen\ Atoms.[/tex]

[tex]Hence,\\Gram\ Molecular\ Mass\ of\ Na_2SO_4=2*(GAM\ of\ Na)+1*(GAM\ of\ S)\\+4*(GAM\ of\ O)\\=2*23+1*32+4*16\\=46+32+64\\=46+96\\=142\ g[/tex]

[tex]Hence,\\We\ also\ know\ that,\\Mass\ of\ A\ Sample=No.\ of\ moles*Gram\ Molecular\ Mass\\Hence,\\Mass\ of\ 29\ moles\ of\ Na_2SO_4=29*142=4118\ g[/tex]

Answer:

4118.2

Explanation:

Given: 29 moles of na²[tex]So^{4}[/tex]

To find: In grams.

Solution: Wrong

If 1 na²[tex]So^{4}[/tex] is 142 grams, then 29 grams will be found if a set of fraction has been set up;

Let [tex]"x"[/tex] be the variable

[tex]\frac{142}{1} = \frac{29}{x}[/tex]

Cross multiply

[tex]\frac{142}{29}[/tex] [tex]= 4.9[/tex]

Correct Solution

Multiply 29 by 142 = 4118

Answer:

Can cause sunburn, premature aging of the skin and damage molecules in skin cells

Explanation:

Answer:

pueden afectar directo al adn de las celulas de la piel y son causantes de las quemaduras del sol

Explanation:

Answer:

25.45 Liters

Explanation:

Using Ideal Gas Law PV = nRT => V = nRT/P

V = (1mole)(0.08206Latm/molK)(298K)/(1atm) = 25.45 Liters

The solutes in a solvent can be make more soluble by heating. Thus upon heating the sugar lumps forming at the bottom of the water can be easily dissolved.

Solubility of substance is the fraction of its concentration which dissolves in a solvent. Solubility is affected by several factors such as temperature, pressure, molecular weight, bond type etc.

Water is known as universal solvent because, it can dissolve almost all the inorganic and organic compounds. The hydroxide ions in water forms hydrogen bonds with compounds and easily dissolve them.

By providing thermal energy the intermolecular attraction of the solute molecules can be weekend and they easily forms bonds with the solvent molecules results in dissolution. Thus option 1 is correct.

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Answer:

Hello

Explanation:

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Answer:

bang on a drum

Explanation:

Answer:

Bang on drum

Explanation:

Its right.

Answer:

Option D, Index fossil helps scientists to determine the relative ages of rocks by their positions

Explanation:

Index fossils are arranged in layer in such a way that the lowest layer represent the oldest fossil and the top most layer represents the youngest fossil. Scientist use this concept to determine the relative age of the rocks based on their position beneath the earth’s surface

Hence, option D is correct

The cheese having a higher thermal conductivity conducts heat better so it can deliver the heat to your mouth more quickly while the pizza crust transmits heat more slowly. So, even if they were the same temperature, the cheese would more likely give your tongue/mouth a severe burn.

Answer:

convection

Explanation:

Convection is a mode of heat transfer in which the particles of a substance actually move from place to place.

During convection, warmer and less dense air rises while colder and denser air sinks downwards under gravity.

Hence; when hot air balloon rises because the fire warms up the air and the air circulates to fill the balloon and lift it at the same time, convection has taken place.

Answer:

Rubidium Chloride is an excellent water soluble crystalline Rubidium source for uses compatible with chlorides.

Compound Formula: ClRb

Melting Point: 715 °C

Boiling Point: 1,390 °C

Explanation:

Answer:

The cell wall surrounds the plasma membrane of plant cells and provides tensile strength and protection against mechanical and osmotic stress. It also allows cells to develop turgor pressure, which is the pressure of the cell contents against the cell wall.

Explanation:

ion

Answer:

7.53*10²³ molecules of oxygen will you need.

Explanation:

Avogadro's Number or Avogadro's Constant is called the number of particles that make up a substance (usually atoms or molecules) that can be found in the amount of one mole of said substance. Its value is 6.023*10²³ particles per mole. Avogadro's number applies to any substance.

You can then apply the following rule of three: if by definition of Avogadro's Number 1 mole of oxygen gas contains 6.023*10²³ molecules, 1.25 moles contains how many molecules?

[tex]amount of molecules=\frac{1.25 moles*6.023*10^{23}molecules }{1 mole}[/tex]

amount of molecules= 7.53*10²³

7.53*10²³ molecules of oxygen will you need.

Answer: it’s D

Explanation:an event that provokes a specific functional response in an organ or tissue of an organism is called as stimulus

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Answer:

The hot temperature of inner core and outer core is responsible for the production of magnetic field.

Explanation:

The physical properties of the inner core, outer core, and lower mantle are essential for the development of Earth's magnetic field because the very high temperature of inner core is responsible for the formation of magnetic field. If the inner core is not very hot so the magnetic field will not be generated and our earth's atmosphere will not be save from the solar wind. It can be blown away by the solar wind if this magnetic field is not present so we can conclude that the physical properties of inner core and outer core is important for the production of magnetic field.

Answer:

Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic information of their parents.

Explanation:

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Answer:

X5Y2

Explanation:

% composition of X = 52.2%

% composition of Y = (100 - 52.2) = 47.8%

This means that there are 52.2g of X and 47.8g of Y in the compound

To calculate the empirical formula of the compound, we first convert the gram value to mole value by dividing by their molar masses.

X = 52.2g/42.3g/mol = 1.234mol

Y = 47.8g/96.7g/mol = 0.494mol

Next, we divide each mole value by the smallest value (0.494mol)

X = 1.234mol ÷ 0.494mol = 2.49

Y = 0.494mol ÷ 0.494mol = 1

We multiply each value by 2

X = 2.49 × 2 = 4.98

Y = 1 × 2 = 2

The simple ratio of X:Y is 5:2, hence, their empirical formula is X5Y2.

Answer:

An acidic solution has a high concentration of hydrogen ions (H +start superscript, plus, end superscript), greater than that of pure water.

The acidic solution indicates the highest concentration of hydrogen or the proton ion in the solution.

Acidity is the measure of the hydrogen ion in the solution by the pH scale and gives the acidic or basic characteristics to the solution.

The concentration of the hydronium or the hydroxide in the solution is a way to determine the acidic basic nature and the pH and pOH of the solution.

Therefore, in an acidic solution hydrogen ions are in the greatest concentration.

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