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3 years ago

Which of these is an indication that a chemical reaction has occurred?

Chemistry

2 answers:

Elena L [17]3 years ago

8 0

A change in color indicates a chemical reaction :)

lilavasa [31]3 years ago

5 0

D. a change in color of a substance

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Which two processes turn layers of loose sediment into hard sedimentary rock? (ASAP)

kvasek [131]

Answer:

compaction and cementation

Explanation:

6 0

3 years ago

When a 18.0 mL sample of a 0.308 M aqueous hydrofluoric acid solution is titrated with a 0.361 M aqueous sodium hydroxide soluti

sleet_krkn [62]

Answer:

pH = 12.8

Explanation:

HF + NaOH → F⁻ + Na⁺ + H₂O

1 mole of HF reacts with 1 mole of NaOH

Initial moles of HF and NaOH are:

HF = 0.018L × (0.308mol / L) = 5.544x10⁻³mol HF

NaOH = 0.023L × (0.361mol / L) = 8.303x10⁻³mol NaOH

That means moles of NaOH remains after reaction are:

8.303x10⁻³mol - 5.544x10⁻³mol = 2.759x10⁻³moles NaOH

Total volume is 18.0mL + 23.0mL = 41.0mL = 0.0410L

Molar concentration of NaOH is

2.759x10⁻³moles NaOH / 0.0410L = 0.0673M = [OH⁻]

pOH = - log [OH⁻] = 1.17

As pH = 14 - pOH

pH = 12.8

4 0

3 years ago

Write the electron dot structures for the following elements:

Evgesh-ka [11]

Answer:

Drawings of Lewis structure Are attached for your elements

Explanation:

Please open the attachment

7 0

3 years ago

How many atoms and elements are there in C2H5OH

Hatshy [7]

Total atoms is 9 ( 2 carbon atoms, 5 hydrogen atoms, 1 oxygen atom and 1 hydrogen atom = 9 atoms)

Element is 3 ( Carbon, Hydrogen and Oxygen)

6 0

3 years ago

The characteristic odor of pineapple is due to ethyl butyrate, a compound containing carbon, hydrogen, and oxygen. Combustion of

gavmur [86]

Answer: The empirical formula for the given compound is $C_3H_6O$

Explanation:

The chemical equation for the combustion of hydrocarbon having carbon, hydrogen and oxygen follows:

$C_xH_yO_z+O_2\rightarrow CO_2+H_2O$

where, 'x', 'y' and 'z' are the subscripts of Carbon, hydrogen and oxygen respectively.

We are given:

Conversion factor: 1 g = 1000 mg

Mass of $CO_2=6.32mg=0.00632g$

Mass of $H_2O=2.58g=0.00258g$

Mass of compound = 2.78 mg = 0.00278 g

We know that:

Molar mass of carbon dioxide = 44 g/mol

Molar mass of water = 18 g/mol

For calculating the mass of carbon:

In 44g of carbon dioxide, 12 g of carbon is contained.

So, in 0.00632 g of carbon dioxide, $\frac{12}{44}\times 0.00632=0.00172g$ of carbon will be contained.

For calculating the mass of hydrogen:

In 18g of water, 2 g of hydrogen is contained.

So, in 0.00258 g of water, $\frac{2}{18}\times 0.00258=0.000286g$ of hydrogen will be contained.

Mass of oxygen in the compound = (0.00278) - (0.00172 + 0.000286) = 0.000774 g

To formulate the empirical formula, we need to follow some steps:

Step 1: Converting the given masses into moles.

Moles of Carbon = $\frac{\text{Given mass of Carbon}}{\text{Molar mass of Carbon}}=\frac{0.00172g}{12g/mole}=1.43\times 10^{-4}moles$

Moles of Hydrogen = $\frac{\text{Given mass of Hydrogen}}{\text{Molar mass of Hydrogen}}=\frac{0.000286g}{1g/mole}=2.86\times 10^{-4}moles$

Moles of Oxygen = $\frac{\text{Given mass of oxygen}}{\text{Molar mass of oxygen}}=\frac{0.000774g}{16g/mole}=4.83\times 10^{-5}moles$

Step 2: Calculating the mole ratio of the given elements.

For the mole ratio, we divide each value of the moles by the smallest number of moles calculated which is $4.83\times 10^{-5}mol$

For Carbon = $\frac{1.43\times 10^{-4}}{4.83\times 10^{-5}}=2.96\approx 3$

For Hydrogen = $\frac{2.86\times 10^{-4}}{4.83\times 10^{-5}}=5.92\approx 6$

For Oxygen = $\frac{4.83\times 10^{-5}}{4.83\times 10^{-5}}=1$

Step 3: Taking the mole ratio as their subscripts.

The ratio of C : H : O = 3 : 6 : 1

Hence, the empirical formula for the given compound is $C_3H_{6}O_1=C_3H_6O$

3 0

3 years ago