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olga_2 [115]
3 years ago
12

An atom with 19 protons and 18 neutrons is a(n)

Chemistry
1 answer:
Eddi Din [679]3 years ago
8 0

Answer:

A

Explanation:

The number of protons indicates the element so we know it's potassium. To get the number of neutrons you subtract the number of protons (19) from the mass number which for potassium is 39.

39-19=20 neutrons

Because you have 18 neutrons then yours would be an isotope.

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If after heating the reaction between magnesium and hydrochloric acid, the mass of the magnesium chloride and beaker is measured
Allushta [10]

Since the beaker was heated we can asume that only magnesium cloride is left in the beaker, therfore the difference between the beaker with magnesium chloride and the empty beaker give the mass of magnisium chloride:

\text{mass MgCl}_2=massbeakerwithMgCl_2-mass\text{ emprty beaker =37.83 g - 33.95g = 3.8}8g

7 0
1 year ago
What geometry does VSEPR predict for the central atom in NCl3
Archy [21]

Answer:

Tetrahedral electron geometry and trigonal pyramidal molecular geometry.

Explanation:

The Lewis structure is shown in Figure 1.

The central N atom has three bonding pairs and one lone pair, for <em>four electron groups</em>.

VSEPR theory predicts a tetrahedral electron geometry with bond angles of 109.5°.

We do not count the lone pair in determining the molecular shape.

The molecular geometry is trigonal pyramidal (see Figure 2).

5 0
3 years ago
In a sample of oxygen gas at room temperature, the average kinetic energy of all the balls stays constant. Which postulate of ki
Levart [38]

Answer:

Collisions between gas particles are elastic; there is no net gain or loss of kinetic energy.

Explanation:

When a gas is paced in a container, the molecules of the gas have little or no intermolecular interaction between them. There is a lot of space between the molecules of the gas.

The gas molecules move at very high speed and collide with each other and with the walls of container.

The collision of these particles with each other is perfectly elastic hence the kinetic energy of the colliding gas particles do not change.

7 0
3 years ago
At 85°C, the vapor pressure of A is 566 torr and that of B is 250 torr. Calculate the composition of a mixture of A and B that b
Phantasy [73]

Answer:

Composition of the mixture:

x_{A} =0.652=65.2 %

x_{B} =0.348=34.8 %

Composition of the vapor mixture:

y_{A} =0.809=80.9%

y_{B} =0.191=19.1%

Explanation:

If the ideal solution model is assumed, and the vapor phase is modeled as an ideal gas, the vapor pressure of a binary mixture with x_{A} and x_{B} molar fractions can be calculated as:

P_{vap}=x_{A}P_{A}+x_{B}P_{B}

Where P_{A} and P_{B} are the vapor pressures of the pure compounds. A substance boils when its vapor pressure is equal to the pressure under it is; so it boils when P_{vap}=P. When the pressure is 0.60 atm, the vapor pressure has to be the same if the mixture is boiling, so:

0.60*760=P_{vap}=x_{A}P_{A}+x_{B}P_{B}\\456=x_{A}P_{A}+(1-x_{A})P_{B}\\456=x_{A}*(P_{A}-P_{B})+P_{B}\\\frac{456-P_{B}}{P_{A}-P_{B}}=x_{A}\\\\\frac{456-250}{566-250}=x_{A}=0.652

With the same assumptions, the vapor mixture may obey to the equation:

x_{A}P_{A}=y_{A}P, where P is the total pressure and y is the fraction in the vapor phase, so:

y_{A} =\frac{x_{A}P_{A}}{P}=\frac{0.652*566}{456} =0.809=80.9 %

The fractions of B can be calculated according to the fact that the sum of the molar fractions is equal to 1.

7 0
3 years ago
Physical Meaning of pKa Which of the following aqueous solutions has the lowest pH: 0.1 M HCl; 0.1 M acetic acid (pKa = 4.86); 0
ser-zykov [4K]

Answer:

<em>The solution with the lowest pH is 0.1 M HCl.</em>

Explanation:

Since the three solutions have the same concentration (0,1M) it is only necessary to look at the pKa of each solution.

Also, knowing that a higher pKa means a lower Ka, because pKa = -Log (Ka). Thus, a lower Ka means a lower concentration of protons with a higher pH ( pH = -Log [H+].

The HCl doesn't have a pKa because is a strong acid that dissociates completely. Therefore, this solution produces a lower pH. Looking at the pKa of acetic acid and formic acid solutions, the second with the lowest pH is the formic acid solutions and the higher pH is for the acetic acid solution.

3 0
3 years ago
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