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2 years ago

7. What does the mass for each element on the periodic table represent:

Chemistry

1 answer:

____ [38]2 years ago

8 0

Answer:

Explanation:

The mass number (represented by the letter A) is defined as the total number of protons and neutrons in an atom. Consider the table below, which shows data from the first six elements of the periodic table. Consider the element helium. Its atomic number is 2, so it has two protons in its nucleus.

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It has been suggested that the surface melting of ice plays a role in enabling speed skaters to achieve peak performance. Carry

vesna_86 [32]

Explanation:

Relation between pressure, latent heat of fusion, and change in volume is as follows.

$\frac{dP}{dT} = \frac{L}{T \times \Delta V}$

Also, $\frac{L}{T} = \Delta S^{fusion}_{m}$

where, $\Delta V^{fusion}_{m}$ is the difference in specific volumes.

Hence, $\frac{dP}{dT} = \frac{\Delta S^{fusion}_{m}}{\Delta V^{fusion}_{m}}$

As, $\Delta S^{fusion}_{m} = \frac{L}{T} = \frac{6010}{273.15}$ = 22.0 J/mol K

And, $\Delta V^{fusion}_{m} = \frac{M}{d_{H_{2}O}} - \frac{M}{d_{ice}}$ ...... (1)

where, $d_{H_{2}O}$ = density of water

$d_{ice}$ = density of ice

M = molar mass of water = $18.02 \times 10^{-3} kg$

Therefore, using formula in equation (1) we will calculate the volume of fusion as follows.

$\Delta V^{fusion}_{m} = \frac{M}{d_{H_{2}O}} - \frac{M}{d_{ice}}$

= $\frac{18.02 \times 10^{-3}}{997} - \frac{18.02 \times 10^{-3}}{920}$

= $-1.51 \times 10^{-6}$

Therefore, calculate the required pressure as follows.

$\frac{dP}{dT} = \frac{22}{-1.51 \times 10^{-6}}$

= $1.45 \times 10^{7} Pa/K$

or, = 145 bar/K

Hence, for change of 1 degree pressure the decrease is 145 bar and for 4.7 degree change dP = $145 \times 4.7 bar$

= 681.5 bar

Thus, we can conclude that pressure should be increased by 681.5 bar to cause 4.7 degree change in melting point.

5 0

2 years ago

2KCIO3 -2KCL + 302

Firlakuza [10]

Answer:

a. 6 moles of O₂

b. 4.06×10²⁴ molecules of O₂

c. 3.04 g of KCl

Explanation:

Reaction of decomposition is:

2KClO₃ → 2KCl + 3O₂

a. See stoichiometry value

2 moles of potassium chlorate can decompose to 2 moles of potassium chloride and 3 moles of oxygen. Ratio is 2:3

If 2 moles of KClO₃ can decompose to 3 moles of O₂

Then 4 moles, may decompose to (4 . 3)/2 = 6 moles of O₂

b. In this case, the stoichiometry is the same.

Per 2 moles of KClO₃, I produce 2 moles of KCl

Then, 4.5 moles of KCl, were produced by 4.5 moles of KClO₃

We apply, the last relation:

(4.5 . 3) /2 = 6.75 moles of O₂ are also produced.

How many molecules are in 6.75 moles?

6.75 mol . 6.02×10²³ molecules/mol = 4.06×10²⁴ molecules of O₂

c. First of all, we convert the mass to moles:

5g . 1mol /122.55g = 0.0408 moles of salt

As ratio is 2:2, 0.0408 moles of salt, decompose to 0.0408 moles of KCl

We convert the moles to mass: 0.0408 mol . 74.55g /mol = 3.04g

5 0

2 years ago

What type of galaxy is pictured?

andrew-mc [135]

A maybe I’m not sure

7 0

2 years ago

A biochemist carefully measures the molarity of magnesium ion in 47, mL of cell growth medium to be 97. ??. Unfortunately, a car

serg [7]

Complete Question

The complete question is shown on the first uploaded image

Answer:

Answer: 760 uM

Explanation:

the addition of solvent to a solution in a such away that the volume of the solution increases and the concentration decreases is a process know as dilution

The concentration and the volume of the dilute and concentrated solution are given below as follows

$C_{1}V_{1}$ $= C_{f}V_{f}$

Concentrated solution Dilute solution

Given that M1 = 97.0uM

V1 = 47.0 mL

V2 = 6.0 mL

M2 = ?

Therefore M1V1 = M2V2

M2 = M1V1/V2

M2 = (97*47)/6

M2 = 760 uM

Answer: 760 uM

5 0

3 years ago

Hi can someone help me quickly please its for chemistry

lara [203]

Answer:

Explanation:

The atom X has 1 1 protons (atomic number) and thus would have 11 electrons. This means the atom X would have 1 valence electron in it's outermost shell. While the atom Y has 17 protons (atomic number) and thus would have 17 electrons. This means the atom Y would have 7 electrons in it's outermost shell.

The type of bond this atoms (X and Y) would form is an Ionic (or electrovalent) bond. <u>This bond/combination involves the transfer of electron(s) and a molecule is not formed</u> as seen in the image below.

3 0

2 years ago