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Lubov Fominskaja [6]
2 years ago
9

A family of four lives in a three-bedroom house and uses an average of 900 kWh of electricity per month. The family cools their

house for three months during the summer with two window-unit air conditioners that each use 350 kWh of electricity per month. Which of the following is the percentage of the family’s total annual electricity that is used to run the two air conditioners for the three summer months?
9,7%

19.4%

38.8%

77.8%
Chemistry
1 answer:
agasfer [191]2 years ago
5 0
<h2>Answer:</h2><h2>The percentage of the family’s total annual electricity that is used to run the two air conditioners for the three summer months = 19.4 %</h2>

Explanation:

Average electricity consumed per month = 900 kWh

The family cools their house for three months during the summer with two window-unit air conditioners

The power consumed by one window-unit air conditioners = 350 kWh

The power consumed by two window-unit air conditioners = 350(2) = 700 kWh

Power consumed for two air conditioners for the three summer months = 700 (3) = 2100 kWh

Total power consumed for 1 year = 900 (12) = 10800kWh

The percentage of the family’s total annual electricity that is used to run the two air conditioners for the three summer months = \frac{2100}{10800}100 = 19.4 %

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5 0
1 year ago
1) How many aluminum atoms are there in 3.50 grams of Al2O3?
drek231 [11]

Answer:

Aluminium atoms =  4.13 *10^22 aluminium atoms

The correct answer is E

Explanation:

Step 1: Data given

Mass of Al2O3 = 3.50 grams

Molar mass of Al2O3 = 101.96 g/mol

Number of Avogadro = 6.022 * 10^23 /mol

Step 2: Calculate moles Al2O3

Moles Al2O3 = mass Al2O3 / molar mass Al2O3

Moles Al2O3 = 3.50 grams / 101.96 g/mol

Moles Al2O3 = 0.0343 moles

Step 3: Calculate moles Aluminium

In 1 mol Al2O3 we have 2 moles Al

in 0.0343 moles Al2O3 we have 2*0.0343 = 0.0686 moles Al

Step 4: Calculate aluminium atoms

Aluminium atoms =  moles aluminium * Number of Avogadro

Aluminium atoms =  0.0686 * 6.022 * 10^23

Aluminium atoms =  4.13 *10^22 aluminium atoms

The correct answer is E

3 0
2 years ago
A 600.0 mL sample of 0.20 MHF is titrated with 0.10 MNaOH. Determine the pH of the solution after the addition of 600.0 mL of Na
Leona [35]

Answer: pH=12.69

Explanation:

{\text{Moles of HF}=Molarity\times {\text{Volume of solution in liters}}

{\text{Moles of HF}=0.20M\times 0.6L=0.12 moles

HF\rightarrow H^++F^-

Initial 0.12               0       0

Eqm   0.12-x           x        x

K_a=\frac{[H^+][F^-]}{[HF]}

3.5\times 10^{-4}=\frac{x^2}{0.12-x}  

(neglecting small value of x in comparison to 0.12)

x=4.2\times 10^{-5}

Moles of H^+=4.2\times 10^{-5}

NaOH\rightarrow Na^++OH^-

{\text{Molesof NaOH}}=Molarity\times {\text{Volume of solution in liters}}

{\text{Moles of NaOH}}=0.10M\times 0.6L=0.06 moles

0.06 moles of NaOH will give 0.06 moles of [OH^-]

Now 4.2\times 10^{-5} moles of OH^- will be neutralized by 4.2\times 10^{-5} moles of H^+ and (0.06-4.2\times 10^{-5})=0.059 moles of OH^- will be left.

Molarity of OH^-=\frac{0.059moles}{1.2L}=0.049M

pOH=-\log[OH^-]=-\log[0.049]=1.31

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The effective nuclear charge Z_{eff} of an atom is defined as the net positive charge which is felt by the valence electron of the atomic element.

When Z_{eff} is observed to decrease, it is seen that the atomic radius grows in size. So, it explains the inverse relationship between both. This phenomenon occurs, because there is more screening of the electrons from the nucleus taking place, which is observed due to decrease the attraction between the electron and the nucleus.

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