All categories

3 years ago

Which element has exactly ﬁve electrons in the highest principal energy level (the outer shell)?

1 answer:

4 0

Boron (B) has 3 electrons in the outer shell.
Barium (Ba) has 2 electrons.
Phosphorus (P) has 5 electrons.
Manganese (Mn) has 2 electrons.

The answer is C) P (phosphorus).

You might be interested in

The electron configuration of an element is 1s^ 2 2s^ 2 2p^ 2 How many valence electrons does the clement have? (1 point )

Monica [59]

Answer:

Explanation:

8 0

3 years ago

A system gains 687 kJ of heat, resulting in a change in internal energy of the system equal to 156 kJ. How much work is done?

Maslowich

Answer:

w = -531 kJ

1. Work was done by the system.

Explanation:

Step 1: Given data

Heat gained by the system (q): 687 kJ (By convention, when the system absorbs heat, q > 0).

Change in the internal energy of the system (ΔU°): 156 kJ

Step 2: Calculate the work done (w)

We will use the following expression.

ΔU° = q + w

w = ΔU° - q

w = 156 kJ - 687 kJ

w = -531 kJ

By convention, when w < 0, work is done by the system on the surroundings.

4 0

2 years ago

A certain substance X has a normal freezing point of -6.4 C and a molal freezing point depression constant Kf= 3.96 degrees C.kg

Brut [27]

Answer: $1.0\times 10^2g$

Explanation:

Depression in freezing point is given by:

$\Delta T_f=i\times K_f\times m$

$\Delta T_f=T_f^0-T_f=(-6.4-(13.6))^0C=7.2^0C$ = Depression in freezing point

i= vant hoff factor = 1 (for non electrolyte like urea)

$K_f$ = freezing point constant = $3.96^0C/m$

m= molality

$\Delta T_f=i\times K_f\times \frac{\text{mass of solute}}{\text{molar mass of solute}}\times \text{weight of solvent in kg}}$

Weight of solvent (X)= 950 g = 0.95 kg

Molar mass of non electrolyte (urea) = 60.06 g/mol

Mass of non electrolyte (urea) added = ?

$7.2=1\times 3.96\times \frac{xg}{60.06 g/mol\times 0.95kg}$

$x=1.0\times 10^2g$

Thus $1.0\times 10^2g$ urea was dissolved.

8 0

3 years ago

which of these is a environmental effect of burning fossil fuels? A- temperature increase B-soil erosion C-habitat succesion D-F

hoa [83]

Answer:

Explanation:

temperature increase because burning causes heat therefore the planet heats up from all the fossil fuels burned aka "global warming"

3 0

3 years ago

Chemical formula for sodium and sulfur

Nookie1986 [14]

The chemical formula for sodium and sulfur is Na2S I believe...

8 0

2 years ago