Question

1）Ethane gas is composed of carbon and hydrogen. Its decomposition produces 4 parts by mass of carbon to 1 part by mass of hydrogen. The relative mass of carbon atoms is 12 and that of hydrogen atoms is 1. Find out how many hydrogen atoms are combined with each carbon atom in ethane. Show all your work.

2 ）Convert the following:

a 114 ps to s

b 67.2 mm³ to mL

c 17.2 ng to Mg

3）What is the mass number of Tungsten if it has 107 neutrons in its nucleus?

4）How many electrons are there in an atom of K?

Answer 1

2C + 3H2 ------------> C2H6

C2H6 --------------> 2C    +    3H2

                             2*12g      3*2g

C: H   = 24 :6

          = 4 :1

2. 114 ps to s

1 ps = 10^-12 s

114Ps = 114*10^-12 s = 1.14*10^-10 s

b 67.2 mm³ to mL

67.2 mm^3

1mm^3 = 0.001ml

67.2mm^3 = 67.2*0.001ml   = 0.0672ml

c 17.2 ng to Mg

1nano gram = 10^-15 mega grams

17.2ng = 17.2*10^-15 Mg

             = 1.72*10^-14 Mg

3.atomic number of Tungsten = 74

no of protons in Tungsten    = 74

mass of Tungsten                   = P + n

                                               = 74+107   = 181

4. atomic number of K = 19

in neutral atom contains equal number of protons and electrons

19 electrons are present in K