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ValentinkaMS [17]

3 years ago

5

Даю 90 баллов, помогите

1 answer:

aleksklad [387]3 years ago

5 0

Answer:

MgCO3, Ca(OH)2, AgNO3

Explanation:

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Calculate the wavelength, in nanometers, of the light emitted by a hydrogen atom when its electron falls from the n = 7 to the n

Gre4nikov [31]

Answer:

The wavelength of the light emitted by a hydrogen atom for the given transition is 2166 nm.

Explanation:

The energy of nth energy levels of the H atom is given as:

$E_n = -2.18 \times 10^{-18} \times \frac{1}{n^2} J$

Energy of the seventh energy level = $E_7$

$E_7=-2.18 \times 10^{-18} \times \frac{1}{7^2} J$

$E_7=-2.18 \times 10^{-18} \times \frac{1}{7^2} J=-4.4490\times 10^{-20} J$

Energy of the seventh energy level = $E_4$

$E_4=-2.18 \times 10^{-18} \times \frac{1}{4^2} J$

$E_4=-2.18 \times 10^{-18} \times \frac{1}{16} J=-1.3625\times 10^{-19} J$

Energy of the light emitted will be equal to the energy difference of the both levels.

$E=E_7-E_4=-4.4490\times 10^{-20} J-(-1.3625\times 10^{-19} J)$

$E=9.176\times 10^{-20} J$

Wavelength corresponding to energy E can be calculated by using Planck's equation:

$E=\frac{hc}{\lambda }$

$\lambda =\frac{hc}{E}=\frac{6.626\times 10^{-34} Js\times 3\times 10^8 m/s}{9.176\times 10^{-20} J}=2.166\times 10^{-6} m=2166 nm$

The wavelength of the light emitted by a hydrogen atom for the given transition is 2166 nm.

8 0

2 years ago

Chlorine can be prepared in the laboratory by the reaction of manganese dioxide with hydrochloric acid, HCl(aq)HCl(aq), as descr

ra1l [238]

Answer: 0.887 g of $MnO_2$ should be added to excess HCl(aq).

Explanation:

According to ideal gas equation:

$PV=nRT$

P = pressure of gas = 805 torr = 1.06 atm (760torr=1atm)

V = Volume of gas = 235 ml = 0.235 L

n = number of moles = ?

R = gas constant = $0.0821Latm/Kmol$

T =temperature = $25^0C=(25+273)K=298K$

$n=\frac{PV}{RT}$

$n=\frac{1.06atm\times 0.235L}{0.0820 L atm/K mol\times 298K}=0.0102moles$

$MnO_2(s)+4HCl(aq)\rightarrow MnCl_2(aq)+2H_2O(l)+Cl_2(g)$

According to stoichiometry:

1 mole of chlorine is produced by = 1 mole of $MnO_2$

Thus 0.0102 moles of chlorine is produced by = $\frac{1}{1}\times 0.0102=0.0102$ moles of $MnO_2$

Mass of $MnO_2$ = $moles\times {\text {Molar mass}}=0.0102mol\times 87g/mol=0.887g$

0.887 g of $MnO_2$ should be added to excess HCl(aq).

7 0

3 years ago

For each of the processes, determine whether the entropy of the system is increasing or decreasing. The system is underlined.

defon

1. Increasing
2. Increasing
3. Decreasing
4. Increasing
5. Decreasing

6 0

3 years ago

What is the difference between ionic compund and covalent compound

sleet_krkn [62]

A covalent bond is formed between two non-metals that have similar electronegativities.

An <em>i</em><em>o</em><em>n</em><em>i</em><em>c</em><em> </em><em>b</em><em>o</em><em>n</em><em>d</em> is formed between a metal and a non-metal. Non-metals(-ve ion) are "stronger" than the metal(+ve ion) and can get electrons very easily from the metal. These two opposite ions attract each other and form the ionic bond.

5 0

3 years ago

Cacl2 is an example of

11111nata11111 [884]

An ionic bond because ca is a metal and cl is a nonmetal which is an ionic bond

5 0

2 years ago