50 + 50 - 25 x 0 + 5 + 5 =​

Chemical Changes

Chemical changes take place at the molecular level. A chemical change produces a new substance. Another way to think of it is that a chemical change accompanies a chemical reaction. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water.

Physical Changes

Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance, although the starting and ending materials may look very different from each other. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle.

How to Tell Chemical & Physical Changes Apart

A chemical change makes a substance that wasn't there before. There may be clues that a chemical reaction took places, such as light, heat, color change, gas production, odor, or sound. The starting and ending materials of a physical change are the same, even though they may look different.

hope this helps

5 star and brainliest?

Answer:

The molarity of the acid, H₂SO₄ is 3.57 M

Explanation:

We'll begin by writing the balanced equation for the reaction. This is illustrated below:

H₂SO₄ + 2NaOH —> Na₂SO₄ + 2H₂O

From the balanced equation above,

Mole ratio of the acid, H₂SO₄ (nₐ) = 1

Mole ratio of the base, NaOH (n₆) = 2

Finally, we shall determine the molarity of the acid, H₂SO₄. This can be obtained as follow:

Volume of base, NaOH (V₆) = 38.70 cm³

Molarity of base, NaOH (M₆) = 1.90M

Volume of acid, H₂SO₄ (Vₐ) = 10.30 cm³

Molarity of acid, H₂SO₄ (Mₐ) =?

MₐVₐ / M₆V₆ = nₐ/n₆

Mₐ × 10.3 / 1.9 × 38.70 = 1/2

Mₐ × 10.3 / 73.53 = 1/2

Cross multiply

Mₐ × 10.3 × 2 = 73.53 × 1

Mₐ × 20.6 = 73.53

Divide both side by 20.6

Mₐ = 73.53 / 20.6

Mₐ = 3.57 M

Thus, the molarity of the acid, H₂SO₄ is 3.57 M

Answer:

Ba(OH)2 + H2SO3 = BaSO3 + H2O -

Explanation:

The question is incomplete, the complete question is;

A student prepared several aqueous sodium chloride (NaCl) solutions to observe boiling point elevation at various molal concentrations, however, several errors were made throughout the procedure. Determine whether these errors would cause the observed boiling point to be increased or decreased relative to the expected boiling point, based on the procedure, or have no effect on the experimental results.

* The flask is washed with water but not thoroughly dried before preparing the solution

* The mass of NaCl used to prepare the solution is 5.400 grams instead of 4.400 grams

* Some of the prepared solution splashes out of the flask prior to observation of the boiling point

* When making the salt solution, 55.0 milliliters of water is added instead of 50.0 milliliters

Answer:

The flask is washed with water but not thoroughly dried before preparing the solution  - decrease

The mass of NaCl used to prepare the solution is 5.400 grams instead of 4.400 grams

-increase

Some of the prepared solution splashes out of the flask prior to observation of the boiling point- have no effect

When making the salt solution, 55.0 milliliters of water is added instead of 50.0 milliliters- decrease

Explanation:

If the flask is washed but not dried, then the solution will be further diluted than expected. As a result of this further dilution, the observed boiling point will be less than the expected boiling point because the boiling point depends on the solution's concentration.

If more solute is added than expected, the concentration of the solution is increased and the boiling point also increases above the expected boiling point due to the increase in amount of solute present.

If some of the solution splashes out of the flask prior to boiling, the boiling point is not affected because the concentration of the solution was not altered. The boiling point only changes when the concentration of the solution is changed.

If 55 ml of water is added instead of 50 ml, the solution is now more dilute than expected thereby reducing the concentration of the solution and the boiling point. Remember that, as the concentration of the solution decreases, the boiling point decreases accordingly.

The empirical formula :

C₁₀H₁₆N₄SO₇

Given

6.4 g sample

Required

The empirical formula

Solution

mass C :

= 12/44 x 8.37 g

= 2.28

mass H :

= 2/18 x 2.75 g

= 0.305

mass N = 1.06

mass S :

= 32/64 x 1.23

= 0.615

mass O = 6.4 - (2.28+0.305+1.06+0.615) = 2.14 g

Mol ratio :

= C : H : N : S : O

= 2.28/12 : 0.305/1 : 1.06/14 : 0.615/32 : 2.14/16

= 0.19 : 0.305 : 0.076 : 0.019 : 0.133 divided by 0.019

= 10 : 16 : 4 : 1 : 7

The empirical formula :

C₁₀H₁₆N₄SO₇

Answer:

Mg is the limiting reactant.

52.9 g of FeCl₃, remains after the reaction is complete.

Explanation:

First of all, we state the reaction's equation:

3Mg (s) + 2FeCl₃ (aq) → 2Fe (s) + 3MgCl₂ (s)

We determine the mol of each reactant:

43.5 g . 1mol / 24.3g = 1.79 mol of Mg

247 g . 1mol/ 162.2g = 1.52 mol of Iron (III) chloride.

Ratio is 2:3. 2 mol of chloride need 3 moles of Mg to react,

Then 1.52 moles will react with (1.52 . 3) /2 = 2.29 moles

We have 1.79 moles of Mg and we need 2.29, so the limiting reactant is the Mg.

We confirm the chlorine as the excess reactant:

3 moles of Mg need 2 moles of FeCl₃ to react:

1.79 moles of Mg will react to (1.79 . 2) /3  = 1.19 moles of FeCl₃

We have 1.52 moles of FeCl₃ and we only need 1.19, so it is ok, we said that the FeCl₃ is the excess.

After the reaction goes complete, (1.52 - 1.19) moles of FeCl₃ remains.

1.52 - 1.19 = 0.33 moles. We convert them to mass:

0.33 mol . 162.2g /1mol = 52.9 g

Answer:

The mass of a system does not change during a chemical reaction

Explanation:

Correct Answers

Answer:

120 extracted from the gas

Explanation:

The amount of heat required now to achieve that process is 60 J of heat added to the gas.

The amount of heat required to achieve the process is calculated as follows;

[tex]E = \frac{3}{2} nR\Delta T[/tex]

where;

[tex]E = \frac{3}{2} \times 0.032 \times 8.314 \times (150)\\\\E = 60 \ J[/tex]

Thus, the amount of heat required now to achieve that process is 60 J of heat added to the gas.

Learn more about amount of heat here: https://brainly.com/question/13439286

#SPJ2

Answer:

b) The mass of your total product is greater than your total reactants

Explanation:

Mass of reactants is 20 and product is 25 which never occurrs in real

Answer:

A,

C.

D.

B.

Explanation:

The front vent of a fume hood that assists and maintain proper air circulation is Airfoil

The horizontal flat surface area of the fume hood where experiments are being carried out is Work  Surface.

The main characteristics which demonstrate and describes how substances evaporate rapidly and readily into the thin air while producing a huge amount of vapor is known as Volatile

In front of the fume hood, lies the glass panel whose main purpose is to shield the user from the hazardous substance. This glass panel is known as the Sash.

Answer:

Partial pressures:

PCl₅ = 0.558 atm

PCl₃ = 0.22 atm

Cl₂ = 0.22 atm

Explanation:

From the given information:

The number of moles of PCl₅ associated with the evaporation is:

[tex]n_{PCl_5}= \dfrac {weight \ of \ PCl_5} {M.Wt. \ of \ PCl_5}[/tex]

[tex]n_{PCl_5}= \dfrac {2.69 \ g} {208.5 \ g/mol}[/tex]

[tex]n_{PCl_5}= 0.013 \ mol[/tex]

Temperature of the gas = 250° C = (250 + 273.15) K

= 523.15 K

Using the Ideal gas equation to determine the pressure exerted by the completely vaporized PCl₅

PV = nRT

[tex]P = \dfrac{nRT}{V}[/tex]

[tex]P = \dfrac{0.0013 \ mol \times 0.082 \ Latm^0 K^{-1} . mol ^{-1} \times 523.15 \ K}{1.0 \ L}[/tex]

P = 0.558 atm

Thus, at  250° C, decomposition of PCl₅ occurs.

In the container, PCl₅  decomposes to PCl₃ and Cl₂.

i.e.

[tex]PCl_{5(g)} \to PCl_{3(g)}+ Cl_{2(g)}[/tex]

Using Dalton's Law:

[tex]P_{total } =P_1 + P_2+P_3 +...[/tex]

[tex]P_1 = P_{Total} \times X_1[/tex]

where;

X = mole fraction

Then, the total no. of moles in the container is:

[tex]n = \dfrac{PV} {RT}[/tex]

[tex]n = \dfrac{1\ atm \times 1.0\ L}{0.0821 \ L \ atm \ K^{-1}.mol \times 523.15\ K}[/tex]

n = 0.023 mol

Now, the container contains a total amount of 0.023 mol where initially 0.013 mol are that of PCl₅ and remaining 0.005 mol of PCl₃ and 0.005 mol of Cl₂.

Thus, the partial pressure of  PCl₃  is:

[tex]P__{PCL_3} }= P_{total} \times \dfrac{no. \ of \ moles \ of PCl_5}{total \ no. \ of \ moles}[/tex]

[tex]P__{PCL_3}} = 1 \ atm \times \dfrac{0.005}{0.023}[/tex]

[tex]P__{PCL_3}} = 0.22 \ atm[/tex]

Thus, since the no of moles of PCl₃ and Cl₂ are the same, then the partial pressure for Cl₂ is = 0.22 atm

Answer:

Acidic solution used to clean a crucible

Explanation:

This liquid dissolves alcoholic solvents such as crucible, that is why it was selected as the ideal for cleaning.

Although it would be ideal to know in detail which chemical compound is the one you want to clean so that the cleaning technique has better effectiveness.

WASTE CONTAINER refers to the solvent used to rinse chemicals out of a beaker, and it also refers to the acid solution used to clean a crucible. Water used to rinse the detergent out of a flask refer to the SINK.

In conclusion, WASTE CONTAINER refers to the solvent used to rinse chemicals out of a beaker, and it also refers to the acid solution used to clean a crucible. Water used to rinse the detergent out of a flask refer to the SINK.

Learn more in:

https://brainly.com/question/10281181

Answer:

H₂   +   Cl₂    →    2HCl

Explanation:

The given reaction expression is shown below:

      H₂   +   Cl₂    →    HCl

We are to balance this given reaction expression.

Let us do this mathematically;

       aH₂   +   bCl₂    →    cHCl

Conserving H :  2a  = c

                   Cl:   2b  = c

Now, let a  = 1, c  = 2 , b = 1

So:

            H₂   +   Cl₂    →    2HCl

Answer:

B. The same exact

Explanation:

I think B because in order to be a clone of your parent you have to have the exact same DNA and chromosomes.

Hope this helps :D

A clone has the same exact chromosomes as its parent.

CLONING:

Learn more at: https://brainly.com/question/12483409?referrer=searchResults

Answer:

32.7 g

Explanation:

Step 1: Write the balanced combustion reaction

C₄H₁₀ + 6.5 O₂ ⇒ 4 CO₂ + 5 H₂O

Step 2: Calculate the moles corresponding to 99.0 g of CO₂

The molar mass of CO₂ is 44.01 g/mol.

99.0 g × 1 mol/44.01 g = 2.25 mol

Step 3: Calculate the moles of C₄H₁₀ needed to produce 2.25 moles of CO₂

The molar ratio of C₄H₁₀ to CO₂ is 1:4. The moles of C₄H₁₀ needed are 1/4 × 2.25 mol = 0.563 mol.

Step 4: Calculate the mass corresponding to 0.563 moles of C₄H₁₀

The molar mass of C₄H₁₀ is 58.12 g/mol.

0.563 mol × 58.12 g/mol = 32.7 g

Answer:

B. The temperature of the water when the food sample has finished burning completely.

Explanation:

Heat or thermal energy is a form of energy that transfers from one object to another due to a temperature difference between the objects. The units for heat are joules or calories.

Calorimetry is the measurement of heat energy released or absorbed in a chemical  reaction. A calorimeter is used in calorimetry. The calorimeter operates on the Law of Conservation of Energy which states that energy is never created or destroyed but is transformed from one form to another or between objects.

In food calorimetry, the energy released when food is burned is measured by recording the rise in temperature of water in a calorimeter when a given mass of a food sample is burned completely.

Energy can be calculated using the formula: Q = mc ∆T

where Q = the energy in joules or calories, m = the mass in grams, c = specific heat and ∆T = the change in temperature (final temperature - initial temperature).

The temperature of the water when the food sample has finished burning completely is taken as the final temperature of the water. The sample is allowed to smolder for sometime before recording the final  water temperature. This is because the water temperature will continue to rise after the  flame has gone out.

Answer:

both density is different so we can say nugget is not made by gold

Explanation:

given data

mass m = 7.6 g

volume  v = 7.22 mL to 8.06 mL

density of gold = 19.32 g/cm³

solution

we know that if there is when there is density of gold = density of nugget than we can say it is gold

so here

d = [tex]\frac{m}{v}[/tex]     ........1

here v = (8.06 - 7.22) = 0.84 mL

put here value in eq 1

d = [tex]\frac{7.6}{0.84}[/tex]

d = 9.047 g/ml

so here density is different so we can say it is not by gold

Answer:

evolution

Explanation:

Answer:

because bird species are reproduced sexually

so there would be some variations in every generation.

that's why birds could be different from their ancestors.

Answer:

I don't get it is it even a question?

This question is incomplete, the complete question is;

Consider this reaction:

2H₃PO₄(aq) → p₂o₅(aq) + 3H₂O(aq)

At a certain temperature it obeys this rate law.

rate = ( 46.65 M⁻¹.s⁻¹) [ H₃PO₄ ]²

Suppose a vessel contains H₃PO₄  at a concentration of 0.660 M .

Calculate how long it takes for the concentration of H₃PO₄  to decrease  to 20.0% of its initial value .

You may assume no other reaction is important.

Round your answer to significant digits.

Answer:

time taken is 8.574 × 10⁻⁴ s

Explanation:

Given that;

rate = k[ H₃PO₄ ]²

rate constant k = 46.65 M⁻¹.s⁻¹)

Initial concentration A₀ =  0.660 M { which will be 100%}

final concentration At = 20%

for the concentration of H₃PO₄  to decrease  to 20.0% of its initial value = ?

we know that;

rate constant k =  1/t [ 1/At - 1/A₀ ]

we substitute

46.65 = 1/t [ 1/20 - 1/100 ]

46.65 = 1/t [ 0.04 ]

46.65 = 0.04/t

46.65t = 0.04

t = 0.04 / 46.65

t = 0.0008574  ≈ 8.574 × 10⁻⁴ s

Therefore, time taken is 8.574 × 10⁻⁴ s

Answer:

yes, but its better to drink water

Explanation:

Answer:

An Alkane

Explanation:

Formula of ethane is CH3-CH3

Answer:

Ethane is the second member of

An alkane

Answer:

3.39x10⁻⁹ M

Explanation:

Let's assume we have 1 mL of the stream. With a density of 1.0 g/mL, we would have 1 g of the stream.

Now we calculate the mass of mercury present in 1 g of the stream, using its given concentration (0.68 ppb):

Now we convert that mass into moles, using mercury's atomic mass:

Finally we calculate the molarity of mercury, as we know that there are 3.39x10⁻¹² Hg moles in 1 mL of the stream:

The molecules move faster and farther apart when the state changes from the liquid state to the gaseous state.

The matter exists in different forms in nature. Some substances have a fixed shape like wood and stone and can flow, take the shape of their container such as water, while there are forms of matter that do not have certain shapes or sizes.

In solids, the molecules are closely packed and thus solids have a rigid structure. The compact packing of solids means that the molecules are very close to each other and the molecules do not show movement. The kinetic energy of molecules in the solid is the least.

In liquids, the molecules are some distance away from each other and they show movements. Since the molecules in liquid show significant movement, they have some kinetic energy. The kinetic energy of molecules in the liquid is greater than that of solids.

In gases, the molecules are farther from each other and thus their molecules show large amounts of movement. The kinetic energy in gases is the greatest in comparison to solids and liquids.

Learn more about states of matter, here:

https://brainly.com/question/13233345

#SPJ2

Answer:

I can't see any picture?????

Answer:

1 x 10⁻¹¹moldm⁻³

Explanation:

Given parameters:

pH of the solution  = 11

Unknown:

[H] = ?

Solution:

The hydrogen ion concentration is unknown.

From:

                      PH  = - log[H⁺]  

       So;

                     11 = -log[H⁺]

               [H⁺] = 1 x 10⁻¹¹moldm⁻³

Answer:

This indicates there will be the densest (heaviest) liquid on the bottom of the jar there will be the least dense (lightest) liquid on top. Syrup, glycerin, water, oil, and then alcohol would be on top of the order of liquids from hardest to lightest.

Answer:

5.78 × 10¹⁴ Hz

Explanation:

Step 1: Given and required data

Step 2: Convert "λ" to meters

We will use the conversion factor 1 m = 10⁹ nm.

519. nm × 1 m/10⁹ nm = 5.19 × 10⁻⁷ m

Step 3: Calculate the frecquency of this light

We will use the following expression.

c = λ × ν

ν = c/λ

ν = (3.00 × 10⁸ m/s)/5.19 × 10⁻⁷ m

ν = 5.78 × 10¹⁴ s⁻¹ = 5.78 × 10¹⁴ Hz