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3 years ago

Read the following, and answer the questions below. Remember to read the question carefully.

Chemistry

1 answer:

andreev551 [17]3 years ago

8 0

<h3>Question #1:</h3>

False.

Melting is a type of chemical change.

<h3>Question #2:</h3>

True.

If the substance's atoms change in any way, it is a chemical change.

<h3>Question #3:</h3>

True.

If a substance is broken or torn, it's still the same substance. (Take tearing paper, for example)

<h3>Question #4:</h3>

False.

Take boiling water for example, when you boil water, it is still water, right?

<h3>Question #5:</h3>

False.

<em><u>Every</u></em> chemical or physical change in matter includes change in energy. <u><em>Not most.</em></u>

<h3>Question #6</h3>

True.

Hydrogen peroxide (H2O2), has turned into water (H2O) and oxygen (O). The substance has change chemically, therefore it is an chemical change.

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I hoped this helps! If you have any questions, feel free to ask! ^^

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A chemist dissolves 716.mg of pure potassium hydroxide in enough water to make up 130.mL of solution. Calculate the pH of the so

Natasha_Volkova [10]

<u>Answer:</u> The pH of the solution is 13.0

<u>Explanation:</u>

To calculate the molarity of solution, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}$

Given mass of KOH = 716. mg = 0.716 g (Conversion factor: 1 g = 1000 mg)

Molar mass of KOH = 56 g/mol

Volume of solution = 130 mL

Putting values in above equation, we get:

$\text{Molarity of solution}=\frac{0.716\times 1000}{56g/mol\times 130}\\\\\text{Molarity of solution}=0.098M$

1 mole of KOH produces 1 mole of hydroxide ions and 1 mole of potassium ions

To calculate hydroxide ion concentration of the solution, we use the equation:

$pOH=-\log[OH^-]$

We are given:

[tex[[OH^-]=0.098M[/tex]

Putting values in above equation, we get:

$pOH=-\log(0.098)\\\\pOH=1.00$

To calculate the pH of the solution, we use the equation:

pOH + pH = 14

So, pH = 14 - 1.00 = 13.0

Hence, the pH of the solution is 13.0

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3 years ago

One crystalline form of silica (SiO2) has a cubic unit cell, and from X-ray diffraction data it is known that the cell edge leng

Sav [38]

Answer:

8 Silicon atom are present in unit cell.

16 oxygen atoms are present unit cell.

Explanation:

Number of atoms in unit cell = Z =?

Density of silica = tex]2.32 g/cm^3[/tex]

Edge length of cubic unit cell = a = 0.700 nm = $0.700\times 10^{-7} cm$

$1 nm=10^{-7} cm$

Molar mass of Silica = $28.09 g/mol+16.00\times 2=60.09 g/mol$

Formula used :

$\rho=\frac{Z\times M}{N_{A}\times a^{3}}$

where,

$\rho$ = density

Z = number of atom in unit cell

M = atomic mass

$(N_{A})$ = Avogadro's number

a = edge length of unit cell

On substituting all the given values , we will get the value of 'a'.

$2.32 g/cm3=\frac{Z\times 60.09 g/mol}{6.022\times 10^{23} mol^{-1}\times (0.700\times 10^{-7}cm)^{3}}$

$Z = 8$

1 silicon is 2 oxygen atoms. then 8 silicon atoms will be 16 oxygen atoms.

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Naddik [55]

C + O₂ = CO₂ + 393.5 kJ

1 mol CO₂ - 393.5 kJ
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m(CO₂)=n(CO₂)M(CO₂)

m(CO₂)=1.1436*44.01=50.33 g

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The speed limit on parts of the German autobahn was once set at 286 kilometers per hour (km/h). Calculate the speed limit in mil

ikadub [295]

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Therefore, the speed limit is 178mph.

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NNADVOKAT [17]

Answer:

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