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3 years ago

If density usually increases with decreasing temperature, why does ice float on liquid water? Explain.

Chemistry

1 answer:

zepelin [54]3 years ago

6 0

Answer:

If you continue to cool water past 4 degrees Celsius, its density starts to plummet (you can see this in the graph). At zero degrees, i.e., the temperature at which water turns into ice, the density of water is actually quite low. It turns out that ice has a lower density than water, and any object that has a lower density than the liquid form on which it’s kept (in this case, water) will be able to float!

Explanation:

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Balloons may contain tiny microscopic holes, which allow the gas particles within to escape via effusion. Suppose a 4.30 L ballo

olga55 [171]

Answer:

The balloon filled with Helium will effuse more quickly.

Explanation:

Step 1: Data given

Balloon 1: Has a volume 4.3L , a pressure of 1.68 atm and is filled with 1.21g of Helium

Balloon 2: Has also a volume of 4.3 L and a pressure of 1.68 atm but is filled with 39.63 grams of Xenon

Molar mass of He = 4g/mol

Molar mass of Xe = 131.3 g/mol

Since He is lighter than Xe, the effusion rate for He will be larger than that for Xe, which means the time of effusion for He will be smaller than that for Xe.

The balloon filled with Helium will effuse more quickly.

3 0

3 years ago

Read 2 more answers

What elements and molecules are used in the process of photosynthesis.

babymother [125]

Answer: Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.

Explanation:

8 0

3 years ago

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The radioactive isotope of lead, Pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.

Marina86 [1]

Answer:

Therefore it will take 7.66 hours for 80% of the lead decay.

Explanation:

The differential equation for decay is

$\frac{dA}{dt}= kA$

$\Rightarrow \frac{dA}{A}=kdt$

Integrating both sides

ln A= kt+c₁

$\Rightarrow A= e^{kt+c_1}$

$\Rightarrow A=Ce^{kt}$ [ $e^{c_1}=C$ ]

The initial condition is A(0)= A₀,

$\therefore A_0=Ce^{0.k}$

$\Rightarrow C=A_0$

$\therefore A=A_0e^{kt}$ .........(1)

Given that the $Pb_{209}$ has half life of 3.3 hours.

For half life $A=\frac12 A_0$ putting this in equation (1)

$\frac12A_0=A_0e^{k\times3.3}$

$\Rightarrow ln(\frac12)= 3.3k$ [taking ln both sides, $ln \ e^a=a$ ]

$\Rightarrow k=\frac{ln \frac12}{3.3}$

⇒k= - 0.21

Now A₀= 1 gram, 80%=0.8

and A= (1-0.8)A₀ = (0.2×1) gram = 0.2 gram

Now putting the value of k,A and A₀in the equation (1)

$\therefore 0.2=1e^{(-0.21)\times t}$

$\Rightarrow e^{-0.21t}=0.2$

$\Rightarrow -0.21t= ln(0. 2)$

$\Rightarrow t= \frac{ln (0.2)}{-0.21}$

⇒ t≈7.66

Therefore it will take 7.66 hours for 80% of the lead decay.

3 0

3 years ago

Select all that apply.

serious [3.7K]

A beta particle is an electron and it has a -1 charge and zero mass.

Beta decay by emitting an electron is called as β⁻ decay. When this happens, a neutron of the element converts into a proton by emitting an electron. Hence, the mass of daughter nucleus is same as parent atom but atomic number/number of protons is higher by 1 than atomic number of parent atom.

In a β⁻ decay, the symbol is used as ₋₁⁰β or ₋₁⁰e.
-1 is for charge
 0 is for the mass of the particle

4 0

3 years ago

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Using the Brønsted-Lowry concept of acids and bases, identify the Brønsted-Lowry acid and base in each of the following reaction

Luden [163]

Answer:

1. HSO³⁻(aq) + H₂O(l) → H₂SO₃(aq) + OH⁻(aq)

The Brønsted-Lowry acid is H₂O and the Brønsted-Lowry base is HSO³⁻

2. (CH₃)₃N(g) + BCl₃(g) → (CH₃)₃NBCl₃(s)

There are no Brønsted-Lowry acids and bases in this reaction.

Explanation:

According to the Brønsted-Lowry concept, when an acid (HA) and a base (B) undergoes a chemical reaction, the acid (HA) loses a proton and forms its conjugate base (A⁻), whereas the base gains (B) the proton to form its conjugate acid (HB⁺).

The chemical equation for this reaction is:

HA + B ⇌ A⁻ + HB⁺

Given reactions:

1. HSO³⁻(aq) + H₂O(l) → H₂SO₃(aq) + OH⁻(aq)

The Brønsted-Lowry acid is H₂O and the Brønsted-Lowry base is HSO³⁻

Reason: In this reaction, the acid H₂O loses a proton and forms its conjugate base, OH⁻. Whereas, the base HSO³⁻ gains a proton to form its conjugate acid, H₂SO₃.

2. (CH₃)₃N(g) + BCl₃(g) → (CH₃)₃NBCl₃(s)

There are no Brønsted-Lowry acids and bases in this reaction.

Reason: In this reaction, there is no exchange of proton between the acid and the base.

4 0

3 years ago