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3 years ago

Which of the following is an example of a physical change?

Chemistry

2 answers:

o-na [289]3 years ago

7 0

Answer:

I think b is the correct answer

just olya [345]3 years ago

4 0

Answer:evaporation in a swamp cooler

Explanation:

Evaporation in a swamp cooler simply involves the conversion of water in the liquid state to water in the gaseous state. It is an easily reversible process if the vapour can be collected and condensed. A chemical change involves the formation of a new substance and is not easily reversible. It is a chemical reaction. A dry cell operates by a chemical change which produces voltage in the cell. Digestion involves a series of irreversible chemical reactions catalysed by enzymes. Hence the answer.

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Which of the following acids is the WEAKEST? The acid is followed by its Ka value.HF, 3.5 × 10^-4HNO2, 4.6 × 10^-4HCN, 4.9 × 10^

Mila [183]

Answer:

HCN

Explanation:

There are several factors that can tell us when an acid is stronger than another, which are the following:

1. The Polarity of the X - H Bond

2. Size of the X atom.

3. Charge on the acid.

4. Oxidation state of the central atom

5. Values of Ka and pKa.

From all of this factors, we can see that the exercise is already giving us values of Ka, and also we have different types of acid, not only with the form H - X

So, we will base the force of an acid by it's pKa value.

The pKa value which is calculated with the expression:

pKa = -logKa

pKa is a value that indicates how strong is the acid you are working with. This value can vary depending on factors such the charge of the acid. I f this charge can be easily distributed in resonance structures, the compound is more acidic, and therefore the pKa value is lower.

The lower the pKa, the more acidic the compound is.

So calculating the pKa on every structure we have:

HF: pKa = -log(3.5x10^-4) = 3.46

HNO2: pKa = -log(4.6x10^-4) = 3.34

HCN: pKa = -log(4.9x10^-10) = 9.31

HCOOH: pKa = -log(1.8x10^-4) = 3.74

HClO2: -log(1.1x10^-2) = 1.96

So according to all this values, we can conclude that the weakest acid is the HCN

4 0

3 years ago

Is water used to test cheese for protein

nekit [7.7K]

Answer:

yes

Explanation:

because it help the body hydrate

7 0

2 years ago

Methane gas and chlorine gas react to form hydrogen chloride gas and carbon tetrachloride gas. what volume of hydrogen chloride

Anna71 [15]

The reaction between methane gas and chlorine gas to form hydrogen chloride and carbon tetrachloride, all in their gaseous form can be expressed through the chemical reaction below.

CH₄ + 4Cl₂ --> 4HCl + CCl₄

Let us assume that all the involved gases behaves ideally such that each mole of the gas is equal to 22.4 L.

Through proper dimensional analysis, the volume of the produced hydrogen chloride is calculated,
V(HCl) = (1.69 mL CH₄)(1 L CH₄/ 1000 mL CH₄)(1 mol CH₄/22.4 L CH₄)(4 mols HCl/1 mol CH₄)(22.4 L HCl/1 mol HCl)(1000 mL/1 L)

V(HCl) = 6.76 mL

ANSWER: 6.76 mL

3 0

2 years ago

Dinitrogen oxide (N₂O) gas was generated from the thermal decomposition of ammonium nitrate and collected over water. The wet ga

RideAnS [48]

Answer:

126.73 mL

Explanation:

The total pressure of the gas mixture is the sum of the vapor pressure of its constituents. So, the vapor pressure of N₂O(p) can be calculated:

750 = 18.85 + p

p = 750 - 18.85

p = 731.15 torr

It means that for 731.15 torr, N₂O occupied 130 mL. For the general gas equation, we know that

$\frac{p1V1}{T1} = \frac{p2V2}{T2}$

Where p is the pressure, V is the volume, T is the temperature, 1 is the initial state, and 2 the final state. For the same temperatue (21ºC), the equation results on Boyle's law:

p1V1 = p2V2, so:

731.15x130 = 750xV2

750V2 = 95049.5

V2 = 126.73 mL

4 0

3 years ago

The amplitude of a wave is most directly related to what wave characteristic? Crest length

galina1969 [7]

The amplitude of a wave is most directly related to crest length.

Amplitude means the height of a crest or a trough.

7 0

3 years ago