Question

cao calcium oxide
k2o potassium oxide
n2o dinitrogen oxide
mgo magnesium monoxide
n2o4 dinitrogen tetroxide
a. 1 (only one compound is named correctly.)
b. 2
c. 3
d. 4
e. 5 (all five compounds are named correctly.)

1. what is the molar mass of sodium sulfate?

a. 55.06 g/mol
b. 78.05 g/mol
c. 119.06 g/mol
d. 142.04 g/mol
e. 215.13 g/mol

1. you have two different ions of the element cobalt. which is false about these ions?

a. the two ions may have different numbers of neutrons.
b. the two ions may have different numbers of protons.
c. the two ions may have different numbers of electrons.
d. none of these (a - c) are false regarding these ions; all three statements are true.
e. all of these (a - e) are false regarding these ions.

1. the densities of ethanol and water are 0.789 g/ml and 1.00 g/ml respectively. if 50.0 g samples of each liquid are obtained, which liquid has the larger volume?

(a) the sample of ethanol
(b) the sample of water
(c) both samples have the same volume
(d) more information is needed to compare their volumes

1. the element rhenium, re (atomic number 75), exists in two isotopes: rhenium - 185 and rhenium. which isotope is more abundant?

Explanation:

18.

Step1: Recall naming rules

For binary ionic compounds like CaO, MgO, K₂O, the metal is named first followed by the non - metal with an - ide ending. For molecular compounds like N₂O and N₂O₄, prefixes are used to indicate the number of atoms. CaO is calcium oxide (correct), K₂O should be potassium oxide (correct), N₂O is dinitrogen monoxide (not dinitrogen oxide, incorrect), MgO is magnesium oxide (correct), N₂O₄ is dinitrogen tetroxide (correct). So 4 compounds are named correctly.

Step1: Identify elements in sodium sulfate

Sodium sulfate has the formula Na₂SO₄. Sodium (Na) has an atomic mass of approximately 22.99 g/mol, sulfur (S) has an atomic mass of approximately 32.07 g/mol, and oxygen (O) has an atomic mass of approximately 16.00 g/mol.

Step2: Calculate molar mass

The molar mass of Na₂SO₄ is \(2\times22.99 + 32.07+4\times16.00=45.98 + 32.07+64.00 = 142.05\approx142.04\) g/mol.

Step1: Recall ion properties

Ions of the same element have the same number of protons (since the atomic number is fixed for an element). They can have different numbers of neutrons (isotopes) and different numbers of electrons (which causes the charge). So the statement that the two ions may have different numbers of protons is false.

Answer:

d. 4

19.