Which of these elements has physical and chemical properties most similar to silicon (Si) ?

The frequency of a given region of the electromagnetic spectrum is more than 3 x 1019 HZ. Note that the speed of light is 2.998 x 108 m/s. Which waves are found in this region? A. gamma rays B. visible light C. microwaves D. radio waves E. x-rays

A 425-ml sample of hydrogen is collected above water at 35°c and 763 torr. find the volume of the hydrogen sample when the temperature falls to 23°c, assuming the barometric pressure does not change. (vapor pressures of water : at 35°c, 42.

If methyl orange is added to a substance and it turns the substance red, what does this tell you about the pH of the substance? Would this substance be an acid or a base?

What is any condition in an experiment that can be changed

MnO2 + 4 HCl → Cl2 + MnCl2 + 2 H2O Given 145.7 grams of MnO2, how much hydrochloric acid (HCl) is needed to use up the MnO2 completely (MM in g/mol: MnO2=86.94, HCl = 36.46, Cl2=70.9, MnCl2=125.84, H2O=18.02) ? 244.4 g 10.55 g 145.5 g 1407 g

Hydrochloric acid is purchased in 12 molar concentrations. If I needed 200 ml of 2.0 molar HCl, how many milliliters of the concentrated solution would I need

Which of the following represents a chemical change? Bending a wire Freezing of water Fireworks exploding Melting of a wax candle

5.00 L of a gas is collected at 100K and then allowed to expand to 20.0 L. What must the new temperature be in order to maintain the same pressure? A. 400 °C B. 127 °C C. 223 °C D. 627°C

Before the initial explosion was the matter hot or cold

Which of the following atoms has seven valence electrons? chlorine (Cl) nitrogen (N) manganese (Mn) oxygen (O)