Which of the following statements explains how the fossil record provides evidence that evolution has occurred?

An atom of 14 6 c carbon decays by gamma decay which atom is left after the decay

ladessa [460]

Answer is: carbon.

<span>During gamma emission the nucleus emits radiation without changing its composition, if for example have nucleus with six protons and six neutrons (carbon atom) and after gamma decay there is nucleus with six protons and six neutrons.
Gamma rays are the electromagnetic waves with the shortest wavelengths (1 pm), highest frequencies (300 EHz) and highest energy (1,24 MeV).</span>

7 0

3 years ago

Read 2 more answers

Liquid A and liquid B form a solution that behaves ideally according to Raoult's law. The vapor pressures of the pure substances

Rama09 [41]

Answer:

Vapor pressure of solution → 151.1 Torr

Option 2.

Explanation:

Raoult's Law is relationed to colligative property about vapor pressure. A determined solute, can make, the vapor pressure of solution decreases.

ΔP = P° . Xm

where Xm is the mole fraction of solute, P° (vapor pressure of pure solvent)

and ΔP = Vapor pressure of pure solvent - Vapor pressure of solution.

In order to determine the vapor pressure of solution, we need to determine, the vapor pressure of B and A in the solution

B's pressure = P° B . Xm

When we add A to B, A works as the solute and B, as the solvent.

Vapor pressure of pure B is 135 torr. (P° B)

In order to determine, the Xm, we use the moles of A and B

Xm = 5.3 mol of B / (1.28 + 5.3) → 0.806

B's pressure = 135 Torr . 0.806 → 108.81 Torr

If mole fraction of B is 0.806, mole fraction for A (solute) will be (1 - 0.806)

A's pressure = 218 Torr . 0.194 → 42.3 Torr

Vapor pressure of solution is sum of vapor pressures of solute + solvent.

Vapor pressure of solution = 42.3 Torr + 108.81 Torr → 151.1 Torr

6 0

2 years ago

Which one is an interjection? boo! running people?

12345 [234]

Boo! Is the interjection

8 0

2 years ago

Sodium phosphate and calcium chloride react to form sodium chloride and calcium phosphate. If you have 379.4 grams of calcium ch

barxatty [35]

Answer: 353.6 g.

Explanation:

1) Word equation (given)

Sodium phosphate + calcium choride → sodium chloride + calcium phosphate

2) Balanced chemical equation

2 Na₃PO₄ +3 CaCl₂ → 6 NaCl + Ca₃(PO4)₂

3) Mole ratio

2 moles Na₃PO₄ : 3 moles CaCl₂ : 6 moles NaCl : 1 mole Ca₃(PO4)₂

4) Formula to convert grams to moles

number of moles = mass in grams / molar mass

5) Number of moles of limiting reactant

a) mass in grams = 379.4 g CaCl₂

b) molar mass CaCl₂ = 110.98 g/mol

c) number of moles CaCl₂ = 379.4 g / 110.98 g/mol = 3.419 moles

6) Theoretical yield of Ca₃(PO4)₂

3 moles CaCl₂ / 1 mole Ca₃(PO4)₂ = 3.419 moles CaCl₂ / x ⇒

x = 3.419 × 1 / 3 = 1.140 moles Ca₃(PO4)₂

7) Convert 1.140 moles Ca₃(PO4)₂

a) molar mass Ca₃(PO4)₂ = 310.1767 g/mol

b) mass in grams = number of moles × molar mass = 1.140 moles × 310.1767 g/mol = 353.6 g ← answer.

7 0

3 years ago

A 10 mm Brinell hardness indenter is used for some hardness testing measurements of a steel alloy. a) Compute the HB of this mat

Lady_Fox [76]

Explanation:

(a) The given data is as follows.

Load applied (P) = 1000 kg

Indentation produced (d) = 2.50 mm

BHI diameter (D) = 10 mm

Expression for Brinell Hardness is as follows.

HB = $\frac{2P}{\pi D [D - \sqrt{(D^{2} - d^{2})}]}$

Now, putting the given values into the above formula as follows.

HB = $\frac{2P}{\pi D [D - \sqrt{(D^{2} - d^{2})}]}$ = $\frac{2 \times 1000 kg}{3.14 \times 10 mm [D - \sqrt{((10 mm)^{2} - (2.50)^{2})}]}$

= $\frac{2000}{9.98}$

= 200

Therefore, the Brinell HArdness is 200.

(b) The given data is as follows.

Brinell Hardness = 300

Load (P) = 500 kg

BHI diameter (D) = 10 mm

Indentation produced (d) = ?

d = $\sqrt{(D^{2} - [D - \frac{2P}{HB} \pi D]^{2})}$

= $\sqrt{(10 mm)^{2} - [10 mm - \frac{2 \times 500 kg}{300 \times 3.14 \times 10 mm}]^{2}}$

= 4.46 mm

Hence, the diameter of an indentation to yield a hardness of 300 HB when a 500-kg load is used is 4.46 mm.

5 0

2 years ago