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coldgirl [10]
3 years ago
11

For the reaction: 2H2O2 --> 2H2 + 2O2, what is the total number of moles of O2 produced from the complete decomposition of 8

moles H2O2?
A) 2 moles
B) 4 moles
C) 8 moles
D) 16 moles
Chemistry
1 answer:
Softa [21]3 years ago
4 0
2 H₂O₂ --> 2 H₂ + 2 O₂

2 moles H₂O₂ ------> 2 moles O₂
8 moles H₂O₂ ------> ?

moles O₂ = 8 x 2 / 2

moles O₂ = 16 / 2

= 8 moles

Answer C

hope this helps!
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A student mixed some yellow sulfur powder with some iron filings. She was able to take the iron out of the sulfur by using a mag
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Answer: Chemical change

Explanation:

Physical change is a change in which there is no rearrangement of atoms and thus no new substance is formed. There is only change in physical state of the substance. The change can be reversed using physical methods.

Chemical change is a change in which there is rearrangement of atoms and thus new substance is formed. There may or may not be a change in physical state. The change can only be reversed using chemical methods.

Thus when iron and sulfur are heated in a test tube, the chemical change occurs and thus lead to formation of new substances which could not be separated using magnet.

8 0
3 years ago
Kaila runs competitively. She would like to calculate her average running speed each time she runs. Which data should Kaila reco
Sladkaya [172]

Answer:

Start and end times; distance run.  

Step-by-step explanation:

Average speed = distance/time.

Kaila should record the distance run, the time she started, and the time she ended her run.

The difference between the start and end times gives the time for the run.

If she inserts her numbers into the formula, she will get her average running speed.  

4 0
3 years ago
Which of the following would have the most difficult time holding onto heat?
egoroff_w [7]

Answer:

carbon

Explanation:

cabonis not a conductor of heat

6 0
3 years ago
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A pan containing 20.0 grams of water was allowed to cool from a temperature of 95.0 °C. If the amount of heat released is 1,200
Sedbober [7]

Answer:

81°C.

Explanation:

To solve this problem, we can use the relation:

<em>Q = m.c.ΔT,</em>

where, Q is the amount of heat released from water (Q = - 1200 J).

m is the mass of the water (m = 20.0 g).

c is the specific heat capacity of water (c of water = 4.186 J/g.°C).

ΔT is the difference between the initial and final temperature (ΔT = final T - initial T = final T - 95.0°C).

∵ Q = m.c.ΔT

∴ (- 1200 J) = (20.0 g)(4.186 J/g.°C)(final T - 95.0°C ).

(- 1200 J) = 83.72 final T - 7953.

∴ final T = (- 1200 J + 7953)/83.72 = 80.67°C ≅ 81.0°C.

<em>So, the right choice is: 81°C.</em>

7 0
3 years ago
Brass is a substitutional alloy consisting of a solution of copper and zinc. A particular sample of red brass consisting of 79.0
Bas_tet [7]

<u>Answer:</u> The molality and molarity of zinc in the solution is 4.07 m and 28.11 M respectively.

<u>Explanation:</u>

Solute is the substance which is present in smaller proportion in a mixture and solvent is the substance which is present in larger proportion in a mixture.

We are given:

(m/m) % of Cu = 79 %

This means that 79 g of copper is present in 100 grams of alloy.

(m/m) % of Zn = 21 %

This means that 21 g of zinc is present in 100 grams of alloy.

As, zinc is present in smaller proportion. So, it is solute and copper is the solvent.

  • <u>Calculating molality of zinc:</u>

To calculate molality of the zinc, we use the equation:

Molality=\frac{m_{solute}\times 1000}{M_{solute}\times W_{solvent}\text{ in grams}}

where,

m_{solute} = Given mass of solute (Zinc ) = 21 g

M_{solute} = Molar mass of solute (Zinc) = 65.3 g/mol

W_{solvent} = Mass of solvent (copper) = 79 g

Putting values in above equation, we get:

\text{Molality of Zinc}=\frac{21\times 1000}{65.3\times 79}\\\\\text{Molality of zinc}=4.07m

  • <u>Calculating molarity of zinc:</u>

To calculate volume of a substance, we use the equation:

\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}

Density of solution = 8740kg/m^3=\frac{8740kg\frac{1000g}{1kg}}{1m^3\times \frac{10^6cm^3}{1m^3}}=\frac{8740g}{1000cm^3}=8.740g/cm^3

(Conversion factors used are:  1 kg = 1000 g &  1m^3=10^6cm^3  )

Mass of solution = 100 g

Putting values in above equation, we get:

8.740g/cm^3=\frac{100.0g}{\text{Volume of zinc}}\\\\\text{Volume of zinc}=11.44cm^3

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)}}

We are given:

Molar mass of zinc = 65.3 g/mol

Volume of solution = 11.44cm^3=11.44mL     (Conversion factor:  1cm^3=1mL  )

Mass of zinc = 21.0 g

Putting values in above equation, we get:

\text{Molarity of zinc}=\frac{21\times 1000}{65.3\times 11.44}=28.11M

Hence, the molality and molarity of zinc in the solution is 4.07 m and 28.11 M respectively.

4 0
3 years ago
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