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2 years ago

Why do lakes only freeze at the surface?

Chemistry

1 answer:

ankoles [38]2 years ago

3 0

Answer: b

Explanation:

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Carbon-14 has a half-life of 5,700 years.

Maksim231197 [3]

Answer:

$3.106\ \text{g}$

Explanation:

$t_{1/2}$ = Half-life of carbon = 5700 years

t = Time at which the remaining mass is to be found = 10400 years

$m_0$ = Initial mass of carbon = 11 g

Decay constant is given by

$\lambda=\dfrac{\ln2}{t_{1/2}}$

Amount of mass remaining is given by

$m=m_0e^{-\lambda t}\\\Rightarrow m=m_0e^{-\dfrac{\ln2}{t_{1/2}} t}\\\Rightarrow m=11e^{-\dfrac{\ln 2}{5700}\times 10400}\\\Rightarrow m=3.106\ \text{g}$

The amount of the substance that remains after 10400 years is $3.106\ \text{g}$ .

5 0

2 years ago

Let us write the appropriate equilibria and associate the correction <img src="https://tex.z-dn.net/?f=K_b" id="TexFormula1" tit

rosijanka [135]

Explanation:

The relation between $K_a\&K_b$ is given by :

$K_w=K_a\times K_b$

Where :

$K_w=1\times 10^{-14}$ = Ionic prodcut of water

The value of the first ionization constant of sodium sulfite = $K_{a1}=1.4\times 10^{-2}$

The value of $K_{b1}$ :

$1\times 10^{-14}=1.4\times 10^{-2}\times K_{b1}$

$K_{b1}=\frac{1\times 10^{-14}}{1.4\times 10^{-2}}=7.1\times 10^{-13}$

The value of the second ionization constant of sodium sulfite = $K_{a2}=6.3\times 10^{-8}$

The value of $K_{b2}$ :

$1\times 10^{-14}=6.3\times 10^{-8}\times K_{b1}$

$K_{b1}=\frac{1\times 10^{-14}}{6.3\times 10^{-8}}=1.6\times 10^{-7}$

3 0

2 years ago

A metal weighing 7.101 g is placed in a graduated cylinder containing 33.0 mL of water. The water level rose to the 37.4 mL mark

musickatia [10]

Volume of the metal = change in volume reading
Volume = 37.4 - 33
Volume = 4.4 ml

Density = mass / volume
Density = 7.101 / 4.4
Density = 1.61 g/ml

7 0

2 years ago

What volume of oxygen is needed to react with 20cm3 of ethane?

Anna71 [15]

Answer:

The reaction states that 2 moles of ethane react with 7 moles of oxygen. At standard temperature and pressure conditions (STP), each mole of gas occupies a volume of 22.4 liters. Therefore, 2 moles of ethane occupy liters, and 7 moles of oxygen occupy liters. In other words: 6 liters.

Explanation:

I hope it helps you

7 0

2 years ago

Discuss the shapes of s- orbitals, p-orbitals and d-orbitals.

timurjin [86]

The azimuthal quantum number (l) determines its orbital angular momentum and describes the shape of the orbital.

s-orbitals (for example 1s, 2s) are spherically symmetric around the nucleus of the atom.

p-orbitals are dumb-bell shaped. l = 0,1...n-1, when l = 1, that is p subshell.

d-orbitals are butterfly shaped.

3 0

2 years ago