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ale4655 [162]
3 years ago
11

When a paper towel absorbs water, is it a physical or chemical change?

Chemistry
1 answer:
Nonamiya [84]3 years ago
6 0

Answer:

It is a physical change.

Explanation:

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Which of the following organelles is best compared to a post office? 1.Endoplasmic reticulum 2.Golgi apparatus 3. Nucleus 4. Cel
natita [175]
Golgi apparatus because it packs vesicles and transports them to the parts of cell where they are needed.
6 0
3 years ago
Determine the pH of a solution of 0.00278 M of HClO4. Report the answer to two digits past the decimal.
aleksandrvk [35]

Answer:

The pH of a solution of 0.00278 M of HClO₄ is 2.56

Explanation:

pH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance and is calculated as:

pH= - log [H⁺]= - log [H₃O⁺]

On the other hand , a Strong Acid is that acid that in an aqueous solution dissociates completely. In other words, a strong acid completely dissociates into hydrogen ions and anions in solution.

HClO₄ is a strong acid, so in aqueous solution it will be  totally dissociated. Then, the concentration of protons is equal to the initial concentration of  acid and the pH will be calculated:

pH= - log 0.00278

pH= 2.56

<u><em>The pH of a solution of 0.00278 M of HClO₄ is 2.56</em></u>

8 0
3 years ago
The graph below shows how the amount of carbon dioxide (CO2) in our atmosphere has changed since 1960. A graph that plots the am
fenix001 [56]

Answer:

greenhouse effect

Explanation:

8 0
3 years ago
Gallium is produced by the electrolysis of a solution made by dissolving gallium oxide in concentrated NaOH ( aq ) . Calculate t
Sedbober [7]

Answer:

Approximately 6.30\times 10^{-3}\;\rm mol.

Explanation:

The gallium here is likely to be produced from a \rm NaGaO_2\, (aq) solution using electrolysis. However, the problem did not provide a chemical equation for that process. How many electrons will it take to produce one mole of gallium?

Note the Roman Numeral "\mathtt{(III)}" next to \rm Ga.  This numeral indicates that the oxidation state of the gallium in this solution is equal to +3. In other words, each gallium atom is three electrons short from being neutral. It would take three electrons to reduce one of these atoms to its neutral, metallic state in the form of \rm Ga\, (s).

As a result, it would take three moles of electrons to deposit one mole of gallium atoms from this gallium \mathtt{(III)} solution.

How many electrons are supplied? Start by finding the charge on all the electrons in the unit coulomb. Make sure all values are in their standard units.

t = \rm 80.0\; min = 80.0\; min \times 60\;s \cdot min^{-1} = 4800\; s.

Q = I \cdot t = \rm 0.380 \; A \times 4800 \; s = 1.824\times 10^3\; C.

Calculate the number of electrons in moles using the Faraday's constant. This constant gives the size of the charge (in coulombs) on each mole of electrons.

\begin{aligned} n(\text{electrons}) &= \frac{Q}{F} \cr &= \rm \dfrac{1.824\times 10^3\; C}{96485.332\; C \cdot mol^{-1}}\cr &\approx \rm 1.89\times 10^{-2}\; mol \end{aligned}.

It takes three moles of electrons to deposit one mole of gallium atoms \rm Ga\, (s). As a result, \rm 1.89\times 10^{-2}\; mol of electrons would deposit \displaystyle \rm \frac{1}{3}\times 1.89\times 10^{-2}\; mol \approx 6.30\times 10^{-3}\; mol of gallium atoms \rm Ga\, (s).

8 0
2 years ago
Based on the equation, how many grams of Br2 are required to react completely with 36.2 grams of AlCl3?
s2008m [1.1K]

Answer:

65.08 g.

Explanation:

  • For the reaction, the balanced equation is:

<em>2AlCl₃ + 3Br₂ → 2AlBr₃ + 3Cl₂,</em>

2.0 mole of AlCl₃ reacts with 3.0 mole of Br₂ to produce 2.0 mole of AlBr₃ and 3.0 mole of Cl₂.

  • Firstly, we need to calculate the no. of moles of 36.2 grams of AlCl₃:

<em>n = mass/molar mass</em> = (36.2 g)/(133.34 g/mol) = <em>0.2715 mol.</em>

<u><em>Using cross multiplication:</em></u>

2.0 mole of AlCl₃ reacts with → 3.0 mole of Br₂, from the stichiometry.

0.2715 mol of AlCl₃ reacts with → ??? mole of Br₂.

∴ The no. of moles of Br₂ reacts completely with 0.2715 mol (36.2 g) of AlCl₃  = (0.2715 mol)(3.0 mole)/(2.0 mole) = 0.4072 mol.

<em>∴ The mass of Br₂ reacts completely with 0.2715 mol (36.2 g) of AlCl₃ = no. of moles of Br₂ x molar mass</em> = (0.4072 mol)(159.808 g/mol ) = <em>65.08 g.</em>

4 0
3 years ago
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