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Questions in chemistry

[Terjawab] The table below gives the numbers of protons, electrons, and neutrons in four atoms. | Atom | Number of protons | Number of neutrons | Number of electrons | |---|---|---|---| | 1 | 9 | 8 | 9 | | 2 | 9 | 9 | 8 | | 3 | 9 | 9 | 10 | | 4 | 9 | 10 | 9 | Based on the table, which atom has a charge of -1?

[Terjawab] Which of the following notations is the correct noble gas configuration for Co? A. $[Ar] 4s^2 4p^6 3d^1$ B. $[Kr] 4s^2 4p^6 4d^1$ C. $[Co] 4s^2 3d^7$ D. $[Ar] 4s^2 3d^7$

[Terjawab] How is the [tex]$\Delta H_{\text {vap }}$[/tex] used to calculate the mass of liquid boiled by 1 kJ of energy? A. [tex]$1 kJ \times \Delta H_{\text {vap }} \times g / mol \text{ liquid}$[/tex] B. [tex]$1 kJ \times 1 / \Delta H_{\text {vap }} \times g / mol$[/tex] liquid C. [tex]$1 kJ \times 1 / \Delta H_{\text {vap }} \times mol / g$[/tex] liquid D. [tex]$1 kJ \times \Delta H_{\text {vap }} \times mol / g$[/tex] liquid

[Terjawab] Number of electrons present in 8.4 g of CO is: A. 0.3 N_A B. 1.4 N_A C. 2.8 N_A D. 4.2 N_A

[Terjawab] Practice Exercise 2. Three isotopes of silicon occur in nature: 28Si (92.23%), atomic mass 27.97693 amu; 29Si (4.68%), atomic mass 28.97649 amu; and 30Si (3.09%), atomic mass 29.97377 amu. Calculate the atomic weight of silicon.

[Terjawab] Find the molality and molarity of 15% H₂SO₄ if the density is 0.020 gram per cubic centimeter.

[Terjawab] Identify the substances that are likely to dissociate in water. Check all that apply. * sodium bromide ([tex]$NaBr$[/tex]) * potassium hydroxide ([tex]$KOH$[/tex]) * magnesium chloride ([tex]$MgCl_2$[/tex]) * silicon dioxide ([tex]$SiO_2$[/tex]) * sodium oxide ([tex]$Na_2O$[/tex])

[Terjawab] An electric device delivers a current of [tex]$15.0 A$[/tex] for 30 seconds. How many electrons flow through it?

[Terjawab] If the pressure, volume, and the number of moles of a gas are known, which is needed to calculate the universal gas constant from the ideal gas law? A. the temperature of the gas B. the molar volume of the gas C. the molar mass of the gas D. the partial pressure of the gas

[Terjawab] Complete the reactions: (i) 2 (CH₃)₂CHCl + 2Na \xrightarrow{dry ether} ? (ii) 2 CH₃-CH(Cl)-CH₂-CH₃ + 2Na \xrightarrow{dry ether} ?