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Questions in chemistry

[Homework Help] 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.

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

[Homework Help] 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])

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

[Homework Help] 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

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

[Homework Help] Which is an intensive property of a substance? A. density B. volume C. length D. mass

[Homework Help] Which of the following particle analysis methods is used to measure the volume of particles? A. Microscopy B. Sedimentation C. Coulter-counter D. Sieving

[Homework Help] Consider the reaction: [tex]2 SO_2(g)+O_2(g) \longleftrightarrow 2 SO_3(g)[/tex] When does the given chemical system reach dynamic equilibrium? A. When the rate of the forward reaction is higher that the rate of the reverse reaction B. When the concentration of the reactants is high than the concentration of the products C. When the rates of the forward and reverse reactions are equal

[Homework Help] What does a pH of 7 say about a solution? A. The solution is acidic. B. The solution is at equilibrium. C. The solution is basic. D. The solution is neutral.