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3 years ago

8. A log is burning in a fireplace. If the amount of oxygen reaching the log is decreased, which of the

2 answers:

8 0

Answer: the reaction rate decreases.

Fire is the result of a combustion reaction, which is the reactionof the organic matter with oxygen. The rate is proportional to amountof oxygen. The, when the amount of oxygen that reaches the organic matter decreases, the rate of combustion decreases too.

EastWind [94]3 years ago

3 0

Answer is: The reaction rate decreases.

Balanced chemical reaction of burning log:

C(s) + O₂(g) → CO₂(g).

The reaction rate is the speed at which reactants are converted into products.

Reaction rate depends on concentration (amount) of oxygen.

If amount of oxygen decreases, reaction rate also decreases and vice versa.

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Purification of copper can be achieved by electrorefining copper from an impure copper anode onto a pure copper cathode in an el

Dovator [93]

Answer: 406 hours

Explanation:

$Q=I\times t$

where Q= quantity of electricity in coloumbs

I = current in amperes = 39.5 A

t= time in seconds = ?

The deposition of copper at cathode is represented by:

$Cu^{2+}+2e^-\rightarrow Cu$

$96500\times 2=193000$ Coloumb of electricity deposits 1 mole of copper

i.e. 63.5 g of copper is deposited by = 193000 Coloumb

Thus 19.0 kg or 19000 g of copper is deposited by = $\frac{193000}{63.5}\times 19000=57748032$ Coloumb

$57748032=39.5\times t$

$t=1461975sec=406hours$ (1hour=3600s)

Thus it will take 406 hours to plate 19.0 kg of copper onto the cathode if the current passed through the cell is held constant at 39.5 A

3 0

3 years ago

A 25.00 g solid sample of Ca(OH)2 was added into 1250 mL of 0.400 M HCl aqueous solution. The temperature of the solution was de

daser333 [38]

Answer:

86.735 kJ

Explanation:

Simply multiply the change in temperature by the Ccal;

(36.6 - 20.0)×5.225 = 86.735

5 0

3 years ago

Pls help me with this question

Drupady [299]

The answer is c hopefully I helped you

4 0

3 years ago

Formaldehyde is a carcinogenic volatile organic compound with a permissible exposure level of 0.75 ppm. At this level, how many

Flauer [41]

Answer : The amount of formaldehyde permissible are, $5.4\times 10^{-6}g$

Explanation : Given,

Density of air = $1.2kg/m^3=1.2g/L$ $(1kg/m^3=1g/L)$

First we have to calculate the mass of air.

$\text{Mass of air}=\text{Density of air}\times \text{Volume of air}$

$\text{Mass of air}=1.2g/L\times 6.0L$

$\text{Mass of air}=7.2g$

Now we have to calculate the amount of formaldehyde.

Permissible exposure level of formaldehyde = 0.75 ppm = $\frac{0.75g\text{ of formaldehyde}}{10^6g\text{ of air}}$

Amount of formaldehyde in 7.2 g of formaldehyde = $7.2g\times \frac{0.75g\text{ of formaldehyde}}{10^6g\text{ of air}}$

Amount of formaldehyde in 7.2 g of formaldehyde = $5.4\times 10^{-6}g$

Thus, the amount of formaldehyde permissible are, $5.4\times 10^{-6}g$

8 0

3 years ago

Which of the following indicates that an exothermic reaction has taken place?

Tomtit [17]

<h2>Answer:</h2>

The option B is correct option. Which is release of heat and/or light energy .

<h3>Explanation:</h3>

According to the definition of exothermic reaction :

<em>An exothermic reaction is a chemical reaction that releases energy by light or heat.</em>

From definition option B (release of heat and/or light energy) indicates that an exothermic reaction has taken place.

4 0

3 years ago

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