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4 years ago

2. Why would a calcium (Ca) atom be larger than a bromine (Br) atom even

1 answer:

3 0

Within a period, the atom size decreases with increasing group number (from left to right), since the nuclear charge and the number of external electrons increase within the period, but the number of shells does not. The electrons are more strongly attracted to the nucleus and are therefore closer to the nucleus.

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What is the volume of 0.640 grams of Oz gas at Standard Temperature and Pressure (STP)?

Ilia_Sergeevich [38]

Answer: The volume of 0.640 grams of $O_{2}$ gas at Standard Temperature and Pressure (STP) is 0.449 L.

Explanation:

Given: Mass of $O_{2}$ gas = 0.640 g

Pressure = 1.0 atm

Temperature = 273 K

As number of moles is the mass of substance divided by its molar mass.

So, moles of $O_{2}$ (molar mass = 32.0 g/mol) is as follows.

$No. of moles = \frac{mass}{molar mass}\\= \frac{0.640 g}{32.0 g/mol}\\= 0.02 mol$

Now, ideal gas equation is used to calculate the volume as follows.

PV = nRT

where,

P = pressure

V = volume

n = no. of moles

R = gas constant = 0.0821 L atm/mol K

T = temperature

Substitute the values into above formula as follows.

$PV = nRT\\1.0 atm \times V = 0.02 mol \times 0.0821 L atm/mol K \times 273 K\\V = 0.449 L$

Thus, we can conclude that the volume of 0.640 grams of $O_{2}$ gas at Standard Temperature and Pressure (STP) is 0.449 L.

6 0

3 years ago

What is the molarity of 2.00 L of a solution that contains 14.6 g NaCl?

White raven [17]

Answer: The molarity of the solution is 0.125 M

Explanation:

Molarity of a solution is defined as the number of moles of solute dissolved per liter of the solution.

$Molarity=\frac{n}{V_s}$

where,

n = moles of solute

$V_s$ = volume of solution in L

moles of $NaCl$ = $\frac{\text {given mass}}{\text {Molar mass}}=\frac{14.6g}{58.5g/mol}=0.250mol$

Now put all the given values in the formula of molality, we get

$Molarity=\frac{0.250mol}{2.00L}=0.125M$

Therefore, the molarity of the solution is 0.125 M

8 0

3 years ago

Which option is a valid hypothesis in the correct format?

Rashid [163]

Answer:

4. If cotton plants need a consistent amount of water to grow steadily, then a cotton plant that displays steady growth will receieve 100 mL of water every day.

Explanation:

Hypotheses are written in the format of "If... then...". It should include information on both variables to arrive at a conclusion point.

5 0

3 years ago

Using the Bohr model, determine the energy, in joules, necessary to ionize a ground-state hydrogen atom. Show your calculations.

lord [1]

Answer:

The energy required to ionize the ground-state hydrogen atom is 2.18 x 10^-18 J or 13.6 eV.

Explanation:

To find the energy required to ionize ground-state hydrogen atom first we calculate the wavelength of photon required for this operation.

It is given by Bohr's Theory as:

1/λ = Rh (1/n1² - 1/n2²)

where,

λ = wavelength of photon

n1 = initial state = 1 (ground-state of hydrogen)

n2 = final state = ∞ (since, electron goes far away from atom after ionization)

Rh = Rhydberg's Constant = 1.097 x 10^7 /m

Therefore,

1/λ = (1.097 x 10^7 /m)(1/1² - 1/∞²)

λ = 9.115 x 10^-8 m = 91.15 nm

Now, for energy (E) we know that:

E = hc/λ

where,

h = Plank's Constant = 6.625 x 10^-34 J.s

c = speed of light = 3 x 10^8 m/s

Therefore,

E = (6.625 x 10^-34 J.s)(3 x 10^8 m/s)/(9.115 x 10^-8 m)

E = (2.18 x 10^-18 J)(1 eV/1.6 x 10^-19 J)

5 0

4 years ago

Based on the information in the passage, what is true of gases?

luda_lava [24]

1: True
2: True
3: False
4: False

(Question 2 might not be true, not sure)

7 0

3 years ago