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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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Elanso [62]

Answer:

A polar molecule

Explanation:

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2 years ago

How can I balance this equation? TELL ME HOW you did it and all the steps and you will be the brainliest.

lianna [129]

Answer:

3 CH3CH2OH + 4 H2CrO4 + 6 H2SO4 --> 3 CH3COOH + 2 Cr2(SO4)3 + 13 H2O

Explanation:

To balance, start of with the groups that are common on both sides of the reaction equation;

In this case, these are the SO4 groups treating them as single units;

There are 3 on the right side and 1 on the left side, so we put 3 in front of the H2SO4 to balance this first;

Next, deal with the Cr, there are 2 Cr on the right side and 1 on the other side, so we put a 2 in front of the H2CrO4 to balance that;

Thirdly, we notice the C are already balanced as there are 2 on each side so this is fine;

Lastly, we can deal with the O and H;

Bearing in mind the numbers that are in front of the molecules now from prior balancing, there are 9 O and 16 H on the left side and 3 O and 5 H on the right;

7 H2O on the right side would balance the O, but gives us 18 H, which is 2 too many H;

If we were to put 2 in front of the two organic molecules (the ones with C) on either side, we would balance the O by having 6 H2O, but this gives 2 fewer H than necessary;

In order for the H to balance, we need to have 13/2 (or 6.5) H2O, which means we need 3/2 (or 1.5) in front of each organic molecule;

Since, it is not sensible to have 13/2 water molecules or 3/2 organic molecules, we can just multiply everything by 2;

Thus we end up with:

3 CH3CH2OH + 4 H2CrO4 + 6 H2SO4 --> 3 CH3COOH + 2 Cr2(SO4)3 + 13 H2O

Rules of thumb:

- When there are common chemical groups (e.g. SO4) on both sides of a reaction equation, treat them as single units

- Start of with balancing these common groups

- Thereafter, balance the atoms that appear in only one reactant and one product

- Proceed to balance the atoms that appear in more than one reactant or product

- Typically, you should deal with the O and H last

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4 years ago

How many formula units of CaO are in 32.7 g of CaO?

zhuklara [117]

Answer:

D) 3.51x10²³ formula units

Explanation:

To know this, we need to calculate the molecular mass of CaO. To do that, let's use the atomic mass of each element of this compound.

Ca: 40.08 g/mol; O: 16 g/mol

With these given AM, let's calculate the molar mass of CaO:

Mm CaO = 40.08 + 16 = 56.08 g/mol

Now that we have the MM of CaO, it's time to determine the moles of CaO:

moles = mass / MM

moles = 32.7 / 56.08 = 0.5831 moles

Finally to get the formula units, we need to use the Avogadro's number which is 6.02x10²³. According to this number, 1 mole of any substance has this number of atoms, molecules or formula units. So, if we have 0.5831 moles, then the formula units will be:

FU = 0.5831 * 6.02x10²³

<h2>FU = 3.51x10²³ formula units</h2>

Hope this helps

7 0

3 years ago

A student mixed 50 ml of 1.0 M HCl and 50 ml of 1.0 M NaOH in a coffee cup calorimeter and calculated the molar enthalpy change

MrRa [10]

Answer:

-54 kJ/mol

Explanation:

Given that:

A student mixed 50 ml of 1.0 M HCl and 50 ml of 1.0 M NaOH in a coffee cup calorimeter and calculated the molar enthalpy change of the acid-base neutralization reaction to be –54 kJ/mol

i.e

50 ml of 1.0 M HCl + 50 ml of 1.0 M NaOH -----> -54 kJ/mol

If he repeat the same experiment with :

100 ml of 1.0 M HCl + 100 ml of 1.0 M NaOH. ------> ????

From The experiment; the molar enthalpy of change of the acid-base neutralization reaction will be -54 kJ/mol

This is because : The second reaction requires 50 ml in order to neutralize the reaction, then the remaining 50 ml will be excess, Hence, there is no change in the enthalpy of the reaction.

Similarly; we can assume that :

In the first reaction; P moles of is used to liberate Q kJ heat ; then the change in molar enthalpy will be Q/P (kJ/mol).

SO; when he used 100 ml ;

then the amount of moles used is double, likewise the heat liberated will be doubled ;

So;

2P moles is used to liberate 2Q kJ heat ;

2P/2Q = Q/P ( kJ/mol) = -54 kJ/mol

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3 years ago

500 ml of an unknown liquid has a mass of 200g. What is the density of the liquid?

Tom [10]

Answer:

DSS

Explanation:

8 0

3 years ago