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Yuki888 [10]
3 years ago
10

Multiple Questions, Brainliest and 98 points to whoever answers all questions correctly

Chemistry
2 answers:
suter [353]3 years ago
8 0

1

The average atomic  mass  of element  is  84.66

2

symbol    element    protons    neutrons   Electrons   mass No    Atomic No

Cs-133    cesium         55              78            55               133                55

Na-23      sodium         11                12            11                  23                  11

Ne 22       Neon           10              12            1 0                  22                  10        

Au -197     Gold            79             118            79                197                  79

3

The moles of tungsten   that are  in  93.50  grams are  0.509  moles

4

CO2  molecules at STP  are  1.547 x10^23  molecules

 Step  1:  find the  moles of CO2

At  STP    1 mole of a gas= 22.4 l

                                    ?  =5.75 L

all ik

otez555 [7]3 years ago
3 0

<u><em>Question 1</em></u>

The average atomic  mass  of element  is  84.66

<u>calculation</u>

Average  atomic mass is  of an element is the sum of masses of its isotope each  multiplied by its  natural  abundance.

that  is.

[(50.50 x  83.75) /100]   + [( 30.25 x 84.45)/100] + [(,9.25 x 87.40)/100]

=  42.29  +25.55 +16.82=  84.66



<u><em>Question 2</em></u>

fill the table

symbol    element    protons    neutrons   Electrons   mass No    Atomic No

Cs-133    cesium         55              78            55               133                55

Na-23      sodium         11                12            11                  23                  11

Ne 22       Neon           10              12            1 0                  22                  10        

Au -197     Gold            79             118            79                197                  79




<u><em>Question 3</em></u>

The moles of tungsten   that are  in  93.50  grams are 0.509  moles


moles=  mass/molar mass

 molar mass  of  tungsten  = 183.84 g/mol

moles  is therefore=  93.50  g/ 183.84  g/mol=  0.509  moles




<em><u>question  4</u></em>

CO2  molecules at STP  are 1.547 x10^23  molecules

 Step  1:  find the  moles of CO2

At  STP    1 mole of a gas= 22.4 l

                                    ?  =5.75 L

by cross multiplication

=  (5.75 L x 1 mole)/ 22.4 L= 0.257 moles

Step 2:  use the Avogadro's constant  to calculate the number of molecule

that is  1  moles = 6.02 x10^23 molecules

         0.257 moles= ? molecules

by  cross  multiplication

=(0.257 moles x 6.02  x 10^23) / 1 mole  = 1.547 x10^23  molecules



<u><em>question 5</em></u>

The number of calcium  atoms  is 3.82 x10^24  atoms

Step 1:  find the moles  of   calcium

= 253.50 g /40 g/mol= 6.34  moles


Step 2:  use the Avogadro's  law  to calculate the number of atoms.

that is   1 mole= 6.02 x 10^23 atoms

             6.34  moles=  ?  atoms

=6.34 x 6.02 x10^23  = 3.82  x10^24 atoms




<u><em>Question   6</em></u>

mass  in grams  of  NiBr2   is   126.97  grams

Step  1:  by use of  Avogadro's  law  constant  calculate  the  number  of moles


that  is  1 mole = 6.02 x 10^23

                 ?   =   3.50 x  10^23

by  cross  multiplication

= (1  mole  x 3.50  x10^23) /  6.02  x10^23 =0.581 moles

step 2:  calculate the  mass

mass =moles  x  molar mass

=  0.581 moles  x218.53 g/mol = 126.97 grams



 <u><em>Bonus question</em></u>

The molecules of water=  1.00  x10^26 molecules


  calculation

convert liters into  ml

= 3 x 1000  =  3000 ml

find the mass of  water

=  density  x volume

=3000  x0.998  2994  grams

find  the moles of water=mass/molar  mass

= 2994  g/  18  g/mol= 166.33 moles

Use  Avogadro's constant  to  calculate the molecules  of water

that is  1 mole=  6.02 x10^23  molecules

         166.33 moles= ? molecules

= (166.33 moles x6.02 x10^23 molecules) / 1 mole  =  1.00  x10^26  molecules

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