What is the half-life for a substance in

which 25% of the original remains after

10 days?

What is the mass of the most abundant isotope? A. mass number is the mass of the most abundant isotope B. mass number is the mass of the protons in the nucleus C. mass number is the number of protons in the nucleus D.

In terms of energy what kind of system is a sealed glass terrarium on a windsill? A. open B. closed C. destructive D. static

Calculate the wavelength of light emitted when each of the following transitions occur in the hydrogen atom. What type of electromagnetic radiation is emitted in each transition? a. n = 4 → n = 3b. n = 5 → n = 4c. n = 5 → n = 3

The electrolyte in a typical wet storage cell or battery is a mixture of water and A. lead. B. ammonium chloride. C. sulfuric acid. D. zinc.

Which of the following statements about the compound HCl is true? The physical and chemical properties of HCl are different from those of H2 and Cl2. Only the physical properties of HCl are different from those of H2 and Cl2.

Calculate the percent composition of the compound that forms when 222.6 g N combines completely with 77.4 g 0. calculate to the nearest tenth of a percent.

How many moles of hcl will react with 450 mg of Al (OH) 3

Why are two nonpolar substances able to dissolve in each other?

Which of the following illustrates the conservation of matter? A. SnO2 + H2 - -> Sn + 2 H2O B. 2 C + O2 - -> CO2 C. KOH + HBr - -> KBr + H2O D. 6 Cs + N2 - -> 6 Cs3N I want to say B?

AIDS is caused by?