Plz i really need help me in Chem!! ?
please show work so even i know how to do it. THank you in advance. you are saving my life.
1.) At 25 degrees C, the density in air is 0.275 g/L. What volume is occupied by 25 kg of oxygen at 25 degrees C.?
2.) What is the correct answer to the following expression : (18+95) X 0.077351? Carry out the addition operation first. a
a.) 8.7 b.) 8.74 c.) 8.741 d. )8.7407 e.) 8.74066
3.) From the results of his gold foil experiment, Ernest Rutherfors conculed that
a.) electrons have a charge of -1.602 X 10^-19 C.
b.) atoms contain equal numbers of protons and elecrtrons
c.) uranium ores emit a form of radiation that affect photographic plates.
d.) alpha particles are helium nuclei.
e.) atoms are composed of a small, dense nucleus surrounded by a clous of electrons.
4.) An element consists of two isotopes. The abundance of one istope is 95.72% and its atomic mass is 114.9041 u. The atomic mass of the second isotope is 112.9043 u. What is the average atomic mass of the element?
a.) 113.9 u b.) 113.0 u c.) 113.9 u d.) 114.8 u e.) 115.1 u
5.) You have 4.15 g of each of the following elements : Ca, Cu, Ce, Cs, Cf. Which sample contains the largest number of atoms?
6.) the density of lithium is 0.546 g/cm^3. What volume is occupied by 1.96 X 10^23 atoms od lithium?
a.) 0.0859 cm^3 b.) 0.596 cm^3 c.) 4.14 cm ^3 d.) 5.63 cm^3 e.) 39.0 cm^3
7.) A nail is coated with a 0.042 cm thick layer of zinc. The surface area of the nail is 9.17 cm^2. The density of zinc atoms are used in the coating?
a.) 5.0 X 10^20 atoms
b.) 2.5 X 10^22 atoms
c.) 3.3 X 10^22 atoms
d.) 1.7 X 10^ 23 atoms
e.) 1.7 X 10^24 atoms
8.) The density of carbon tetrachloride is 1.59 g/ml. How many chlorine atoms are present in 55 ml. of carbon tetrachloride?
a.) 3.3 X 10^23 atoms
b.) 5.4 X 10^23 atoms
c.) 1.4 X 10^24 atoms
d.) 8.1 X 10^27 atoms
e.) 3.2 X 10^28 atoms
Pleasee do show work. I really need to learn how to do these. Thank you so much in advance
Tags: