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3 years ago

Elements with atomic numbers 7 and 83 have how many valence electrons? *

Chemistry

1 answer:

IRINA_888 [86]3 years ago

5 0

Explanation:

element with atomic numbers 7 and 83 have 5 and 5 valence electrons

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If the concentration of mercury in the water of a polluted lake is 0.250 μg (micrograms) per liter of water, what is the total m

aleksandr82 [10.1K]

Answer:

142.36 kg

Explanation:

volume of water in the lake = surface area x depth

= 18.5 x ( 1760 x 3 )² x 39 ft³

= 2.011 x 10¹⁰ ft³

= 2.011 x 10¹⁰ x 28.3168 liter .

= 56.945 x 10¹⁰ liter .

concentration of mercury = .25 x 10⁻⁶ g / liter

= 25 x 10⁻⁸ g / liter

= 25 x 10⁻¹¹ kg / liter

mass of mercury in the water of lake

= 25 x 10⁻¹¹ x 56.945 x 10¹⁰ kg

= 142.36 kg .

8 0

3 years ago

KNO3(s) --> K+(aq) + NO3-(aq)This reaction was carried out in a Styrofoam insulated calorimeter and the following data were r

nataly862011 [7]

Answer:

Equation correctly showing the heat of solution

$KNO_3(s)+35.2 kJ \rightarrow K^+(aq) + NO_{3}^-(aq)$

Explanation:

Mass of aqueous solution = m = 100 g

Specific heat of solution = c = 4.18 J/gºC

Change in temperature = $\Delta T=T_f-T_i$

ΔT = 21.6ºC - 30.0ºC = -8.4ºC

Heat lost by the solution = Q

$Q = mc\Delta T$

$Q=100 g\times 4.18 J/g^oC\times (-8.4^oC)$

Q = -3,511.2 J ≈ -3.51 kJ

Heat absorbed by potassium nitrate when solution in formed; Q'

Q' = -Q = 3.51 kJ

Moles of potassium nitrate , n= $\frac{10.1 g}{101 g/mol}=0.1 mol$

$KNO_3(s)\rightarrow K^+(aq) + NO_{3}^-(aq)$

The heat of solution =

$\frac{Q'}{n}=\frac{3.5112 kJ}{0.1 mol}=35.1 kJ/mol$

So, the equation correctly showing the heat of solution

$KNO_3(s)+35.2 kJ \rightarrow K^+(aq) + NO_{3}^-(aq)$

4 0

4 years ago

Whats the length of an aluminum rod at 65 c if its length at 15 c is 1.2 meters

Furkat [3]

15c - 1.2m
1c - 1.2/15 = 0.08m
65c - 5.2m

4 0

4 years ago

An atom emits of wavelength 1.08 meters. what is the energy change occurring in the Atom due to this emission? (Planck’s constan

butalik [34]

To answer this question, we can use the following equation:

$e=\frac{h*c}{lambda}$

where e is the energy change, h is Planck's constant, c is the speed of light (m/s), and lambda is wavelength in meters. So then we can plug in the information:

$e=\frac{(6.626x10^{-34}J*s)(2.998x10^{8}\frac{m}{s})}{1.08m}$

$e=\frac{1.9865x10^{-25}J}{1.08}$

$e=1.84x10^{-25}J$

So the energy that is omitted by the atom is $1.84x10^{-25}J$ .

5 0

3 years ago

Refrigerators are usually kept at about 5°C, while room temperature is about 20°C. if you were to take an empty sealed 2 liter s

MakcuM [25]

Answer:

c) No, because Celsius is not an absolute temperature scale

Explanation:

converting 5 oC to kelvin which is the absolute temperature scale gives = 273 + 5 = 278 K

and converting 20 oC to kelvin = 20 + 273 = 293 K

the ratio = 278 / 293 = 0.94 approx 1 not 4

8 0

3 years ago