A chemist is trying to identify an unknown metal, and finds that 25.0 cm³ of the substance has a mass of 224.43 g at 20°C. Which of the following metals is it?

What is the total mass accumulated in a beaker by successive additions of solids in  the amounts 45.65 mg, 8.38 g, and 56840.5 g.  Report your answer in grams, g and  to the correct number of significant figures.   Given: 1 g = 106 g; 1 g = 1000 mg

Calculate the mass of hydrazine (N_2H_4) that contains a billion (1.000 x 10^9) nitrogen atoms. Be sure your answer has a unit symbol if necessary, and round it to significant digits. NOTE: underscore represents the subscript

Calculate the mass of hydrazine (NH4) that contains a trillion (1.00 × 1012) hydrogen atoms. Be sure your answer has a unit symbol if necessary, and round it to 3 significant digits. ☐ ☐ x10

Dr. Dahm has a molecule that has a molecular formula of C18H10O2N3. If he has 12.67 mL of the molecule and its density is 0.842 g/mL calculate how many atoms there are of each type.

Hydrogen peroxide (H2O2) is a mild antiseptic used to prevent infection in minor cuts and scrapes. The density of H2O2 is 1.45 g/mL. The cylinder container that the hydrogen peroxide is stored in has a radius of 8.5 cm and a height of 22 cm. If the container is full, calculate the number of oxygen atoms in the container. (Vcylinder = πr2h).

Calculate the mass of tetraborane (B4H₁0) that contains a million (1.00 x 10°) boron atoms. Be sure your answer has a unit symbol if necessary, and round it to 3 significant digits. x10 X 5 ?

Tia has a sample of pure gold (Au). She weighed the sample and the result was 84.784.7 grams. Tia wants to determine the number of atoms in the sample. Calculate the number of atoms in 84.784.7 g of pure gold.

If a sample of gold alloy has a mass of 87.7 g and is 78.3% gold by mass, what percentage of the alloy is made up of other metals? Write your answer to the nearest tenth of a percent. (I had to alter the wording of this question since it wasn't calculating significant figures properly, so if you got it wrong because of significant figures you can assume you probably actually got it correct.)

Calculate the number of boron atoms in a 120.0 g sample of tetraborane (B4H10). Be sure your answer has a unit symbol if necessary, and round it to 4 significant digits. 0 ☐x10 X Ś