Question

Question 25 (1 point) How many carbon atoms are there in a hydrocarbon chain with no double bonds, where there are ten hydrogen atoms in the molecule? O a) 4 Ob) 6 O O O c) 2 Od) 5 Question 26 (1 point) The compound M2X3 has a molar mass of 160 g/mol. If element X is oxygen, then element M is most likely: O AI. O Ga. O Fe. O Ni. Question 27 (1 point) The measurement that shows three significant digits is: a) 3 050 g Ob) 0.010 g OC) 0.006 g O d) 0.204 g

Answer 1

25. (a) 4

Hydrocarbon chain having no double bonds is an alkane. Alkane has a general formula
CnH2n+2
where 'n' is the number of carbon atoms. So,
2n + 2 = 10
,
10 – 2 n= =

Hence, number of carbon atoms is 4.

26. (c) Fe

X is oxygen, therefore has atomic weight 16 g/mol. So, $X_3$ has weight g/mol.

3 x 16 = 48

The compound
M2X3
has molar mass of 160 g/mol. Mass of $M_2$ can be calculated by subtracting mass of $X_3$ from mass of
M2X3
.

Mass of M2 = 160 – 48 = 112g/mol

112 Mass of M = * = 56g/mol

Fe has an atomic mass of 56g/mol, therefore, the M is most likely to be Fe.

27. (d) 0.204 g

In 3050 there are 4 significant figures. In 0.010 there are 2 significant figures. In 0.006 there is 1 significant figure. There are a set of rules for the determination of signficant figures in a given expression. They can be referred to in any textbook of basic mathematics.