How many moles of atoms are in each elemental sample? A. 1.24 g Zn
B. 28.1 g Ar
C. 84.0 g Ta
D. 2.29x10^-2 g Li

Moles = mass(m) / Molar mass (M)

A. 1.24g of Zn

m = 1.24g

M = 65.4 g/mol

moles of Zn = 1.24g/ 65.4g/mol

= 0.01896mol

B. 28.1 g Ar

m = 28.1g

M(Ar) = 39.9g/mol

moles of Ar = 28.1g/39.9g/mol

= 0.7043 mol

C. 84.0 g Ta

m = 84.0g

M(Ta) = 181g/mol

moles of Ta = 84.0g/181g/mol

= 0.4641 mol

D. 2.29x10^-2 g Li

m = 2.29x10^-2 g

M(Li) = 6.9g/mol

moles of Li = 2.29x10^-2 g / 6.9g/mol

= 0.0033 mol

Hope this helps

when the volume of gas is   changed from   717.73 ml   to 852 ml   the temperature will   change   from 315   c to 452   c

    calculation

this is calculated using the charles law formula

that is,   v1/t1 = v2/t2

          v1=?

        t1 = 315 c   into   kelvin = 315 +273 = 588 k

        v2 = 852   ml

        t2 = 425c + 273 =698 k

make v1   the subject of the formula ( by   multiplying both side by t1)

  v1=( v2 xt1) / t2

v1= (852 ml   x 588 k)/ 698 k= 717.73 ml