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2 years ago

At what temperature does a heat pump become ineffective?

Chemistry

2 answers:

KengaRu [80]2 years ago

7 0

25 degrees to around 43 degress

gtnhenbr [62]2 years ago

4 0

Answer:between 25 and 40 degrees Fahrenheit

Explanation:

Heat pumps do not operate as efficiently when temperatures drop to between 25 and 40 degrees Fahrenheit for most systems. A heat pump works best when the temperature is above 40. Once outdoor temperatures drop to 40 degrees, heat pumps start losing efficiency, and they consume more energy to do their jobs.

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bekas [8.4K]

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3 years ago

What is responsible for the whistling sound that often accompanies fireworks?

liq [111]

The crackling sound Is mainly to do with chemistry, The fireworks are filled with lead oxide, which turns into lead atoms as the firework explodes and heat up—— whistling sounds, the whistle is down to the tube being narrow one, thus rockets make a whistling noise

6 0

3 years ago

Determine whether the following statements describe chemical or physical properties: (a) Oxygen gas supports combustion. (b) Fer

sdas [7]

Explanation:

A change that does not cause any change in chemical composition of a substance is known as a physical change.

For example, mass, density, volume etc are all physical changes.

On the other hand, a change that brings change in chemical composition of a substance is known as chemical change.

For example, combustion, toxicity, reactivity etc are all chemical changes.

Hence, following statements are identified as chemical or physical changes as follows.

(a) Oxygen gas supports combustion : Chemical change

(b) Fertilizers help to increase agricultural production : Chemical change

(d) Lead is denser than aluminum : Physical change

(e) Uranium is a radioactive element : Chemical change

7 0

3 years ago

A 5.325g sample of methyl benzoate, a compound in perfumes , was found to contain 3.758 g of carbon, 0.316 g of hydrogen, and 1.

Alexxandr [17]

Answer: The empirical and molecular formula of the compound is $C_4H_4O$ and $C_8H_8O_2$ respectively

Explanation:

We are given:

Mass of C = 3.758 g

Mass of H = 0.316 g

Mass of O = 1.251 g

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

Step 1: Converting the given masses into moles.

Moles of Carbon = $\frac{\text{Given mass of Carbon}}{\text{Molar mass of Carbon}}=\frac{3.758g}{12g/mole}=0.313moles$

Moles of Hydrogen = $\frac{\text{Given mass of Hydrogen}}{\text{Molar mass of Hydrogen}}=\frac{0.316g}{1g/mole}=0.316moles$

Moles of Oxygen = $\frac{\text{Given mass of oxygen}}{\text{Molar mass of oxygen}}=\frac{1.251g}{16g/mole}=0.078moles$

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 0.078 moles.

For Carbon = $\frac{0.313}{0.078}=4.01\approx 4$

For Hydrogen = $\frac{0.316}{0.078}=4.05\approx 4$

For Oxygen = $\frac{0.078}{0.078}=1$

Step 3: Taking the mole ratio as their subscripts.

The ratio of C : H : O = 4 : 4 : 1

The empirical formula for the given compound is $C_4H_4O$

For determining the molecular formula, we need to determine the valency which is multiplied by each element to get the molecular formula.

The equation used to calculate the valency is:

$n=\frac{\text{Molecular mass}}{\text{Empirical mass}}$

We are given:

Mass of molecular formula = 130 g/mol

Mass of empirical formula = 68 g/mol

Putting values in above equation, we get:

$n=\frac{130g/mol}{68g/mol}=1.9\approx 2$

Multiplying this valency by the subscript of every element of empirical formula, we get:

$C_{(2\times 4)}H_{(2\times 4)}O_{(2\times 2)}=C_8H_8O_2$

Hence, the empirical and molecular formula of the compound is $C_4H_4O$ and $C_8H_8O_2$ respectively

4 0

3 years ago

A balloon has an internal pressure of 1.95 atm and a volume of 5.0 L. If the temperature where the balloon is

patriot [66]

Answer:

13.1 L

Explanation:

Using the combined gas law:

P1V1/T1 = P2V2/T2

Where;

P1 = initial pressure (atm)

P2 = final pressure (atm)

V1 = initial volume (L)

V2 = final volume (L)

T1 = initial temperature (K)

T2 = final temperature (K)

Based on the information provided in this question;

P1 = 1.95 atm

P2 = 0.65 atm

V1 = 5.0 L

V2 = ?

T1 = 20 °C = 20 + 273 = 293K

T2 = -15 °C = -15 + 273 = 258K

Using P1V1/T1 = P2V2/T2

1.95 × 5/293 = 0.65 × V2/258

9.75/293 = 0.65V2/258

0.0333 = 0.00252V2

V2 = 0.0333 ÷ 0.00252

V2 = 13.1 L

5 0

3 years ago