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3 years ago

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

Chemistry

2 answers:

suter [353]3 years ago

8 0

The average atomic mass of element is 84.66

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

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

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

Question 1

The average atomic mass of element is 84.66

calculation

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

Question 2

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

Question 3

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

question 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

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

question 5

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

Question 6

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

Bonus question

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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