At STP, an element that is a brittle solid and a poor conductor of heat and electricity could have an atomic number of

(1) 12 (3) 16

(2) 13 (4) 17

Cobalt fluoride crystallizes in a closest packed array of fluoride ions, with the cobalt ions filling one-half of the octahedral holes. What is the formula of this compound?

What is the identity of the unknown ink? use evidence to support your claim.

MgCO3 (s) → Mgo (s) + CO2 (g) In the chemical reaction above, what state is Mgo in? a. Liquid b. Gas c. Aqueous d. Solid

Devise a detailed experimental procedure to purify ~ 20 grams of benzoic acid that is contaminated with sodium chloride. Justification of the steps (including solubility calculations) that are included in the procedure.

How many significant figures are there in the following numbers: 10.78, 6.78, 0.78? If these were pH values, to how many significant figures can you express the [H]? Explain any discrepancies between your answers to the two questions.

In a laboratory, Carlos places one plate with grape jelly and another plate with cooked brown rice inside an ant farm. The next day, he finds that both plates are filled with ants.

Which statement is true at STP? (The atomic mass of Zn is 65.39 u.)

A sample of gas has a volume of 2.4 L and a pressure of 1.2 atm. What would the pressure of the same gas sample be if the volume is reduced to 1.8L at a constant temperature?

The elements most likely to form more than type of ion are the ... A. Transition metals B. alkali metals C. halogens D. alkaline earth metals

Mole-Mass Conversions How many moles in 28. o grams of Oxygen? What is the mass of 5.0 moles of Iron? Find the number of moles of argon in 452 g of argon. Find the grams in 16.5 mol of Hydrogen.