Chemistry Chapter 2 Examples
How many neutrons are contained in an atom of nickel-60?
According to the periodic table, nickel has the symbol Ni, and the atomic number, Z, of 28. The mass number 60, is equal to the sum of the number of protons and the number of neutrons. The number of protons is equal to the atomic number, 28. Therefore, the number of neutrons is 60-28=32. The atom contains 32 neutrons.
Calculate the atomic weight of chlorine, given that the naturally occurring element consists of 75.53% chlorine-35 (mass = 34.97 u) ad 24.47% chlorine-37 (mass = 36.97 u)
Atomic weight= (%chlorine-35) (mass chlorine -35) + (% chlorine -37) (mass chlorine -37) over 100 (75.53) (34.97 u) + (24.47) (36.97 u) over 100 2641.28 u + 904.66 u over 100 3545.94 u over 100 35.4594 u = 35.46 u (rounded value)
How many helium atoms would balance one oxygen atom on a seesaw
Helium atoms have an atomic weight of 4.003 u. Oxygen atoms have an atomic weight of 16.00 u. Therefore, four helium atoms will balance one oxygen atom.
Determine the molecular weight of CH4N2O
MW = 1(at.wt.C) + 4(at.wt.H) +2(at.wt.N) + 1(at.wt.O) MW= 1(12.01 u) + 4(1.008 u) +2(14.01 u) + 1(16.00 u) = 60.062 u Rounded to four significant figures the answer is 60.06 u
Write a formula for the following compound: Glucose: six carbon (C) atoms, twelve hydrogen (H) atoms, and six oxygen (O) atoms
C6H12O6
How many calcium ions would have to be put on one side of a seesaw to balance one atom of bromine that was placed on the other side
Calcium atoms have an atomic weight of 40.08 u. Bromine atoms have an atomic weight of 79.90 u. Therefore, two calcium atoms would be required to balance one bromine atom.
How many moles of each type of atom are contained in 1 mol of chloroform (CHCl3)
Each chloroform molecule contains one C atom, one H atom, and three Cl atoms. Therefore, 1 mol of CHCl3, contains 1 mol of C atoms, 1 mol of H atoms, and 3 mol of Cl atoms
Write a formula for the following compound: Sulfuric acid: two hydrogen (H) atoms, one sulfur (S) atom, and four oxygen (O) atoms
H2SO4
Write a formula for the following compound: Phosphoric acid: three hydrogen (H) atoms, one phosphorus (P) atom, and four oxygen (O) atoms
H3PO4
How many protons and how many neutrons are contained in an atom with a mass number of 26 and the symbol Mg?
Magnesium (Mg) has an atomic number of 12. The atom contains 12 protons. Since A, the number of protons plus neutrons is equal to 26, the number of neutrons is 26-12, or 14. The atom contains 14 neutrons
Show that samples of magnesium and carbon with the same masses of 9.663 g and 4.774 g, respectively, have a mass ratio of 2.024 and contain the same number of atoms
Mg mass 9.663 g _____________ = __________ = 2.024 C mass 4.774 g
Write a formula for the following compound: Nitrogen dioxide: one nitrogen (N) atom and two oxygen (O) atoms
NO2
The mass percentage of N is given by part mass of N %N = _______ x 100 =____________________________ x 100 total mass of compound
One mol of NH3 weighs 17.0 g and contains 1 mol of N atoms which weighs 14.0 g 14.0 g %N= _________ x 100 = 82.4% 17.0 g
Write a formula for the following compound: Sulfur trioxide: one sulfur (S) atom and three oxygen (O) atoms
SO3
Determine the following using the factor-unit method of calculation and factors obtained from preceding three relationships given for sulfur: The mass in grams of 1.35 mol of S
The known quantity is 1.35 mol of S, and the unit of the unknown quantity is grams of S. The factor comes from the relationship 1 mol S atoms = 32.1 g S 32.1g S 1.35(___________) = 43.3 g S 1
What are the mass number, atomic number, and isotope symbol for an atom that contains 7 protons and 8 neutrons?
The mass number, A, equals the sum of the number of protons and the number of neutrons: A=7+8=15. The atomic number, Z, equals the number of protons: Z=7. According to the periodic table, the element with an atomic number of 7 is nitrogen, with the symbol N. The isotope symbols is 15 N 7