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2 years ago

How many moles are contained in 127 grams of lead?

Chemistry

2 answers:

rjkz [21]2 years ago

8 0

Answer:

18.015

Explanation:

const2013 [10]2 years ago

3 0

Answer: 0.613 moles

Explanation: To convert from grams to moles, you have to use the molar mass provides on the periodic table. The molar mass of lead is 207.2 g/mol. To find the moles, we need to divide the grams of lead by the molar mass. 127/207.2 is equal to about 0.613 moles.

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As a technician in a large pharmaceutical research firm, you need to produce 250. mL of a potassium dihydrogen phosphate buffer

Reika [66]

Answer:

We will need 147.772 mL of KH2PO4 to make this solution

Explanation:

For this case we can give the following equation:

H2PO4 - ⇄ H+ + HPO42-

With following pH- equation:

pH = pKa + log [HPO42-]/[H2PO4-]

7.05 = 7.21 + log [HPO42-]/[H2PO4-]

-0.16 = log [HPO42-]/[H2PO4-]

10^-0.16 = [HPO42-]/[H2PO4-]

0.6918 = [HPO42-]/[H2PO4-]

Let's say the volume of HPO42-= x then the volume of H2PO4- will be 250 mL - x

Since both have a concentration of 1M = 1 mol /L

If we plug this in the equation 0.6918 = [HPO42-]/[H2PO4-]

0.6918 = x / (250 - x)

0.6918*250 - 0.6918x = x

172.95 = 1.6918x

x = 102.228 mL

The volume of HPO42- = 102.228 mL

Then the volume of H2PO4- = 250 - 102.228 = 147.772 mL

To control this we can plug this in the pH equation

7.05 = 7.21 + log [HPO42-]/[H2PO4-]

7.05= 7.21 + log (102.228 / 147.772) = 7.05

We will need 147.772 mL of KH2PO4 to make this solution

3 0

3 years ago

Which statement best describes the properties of covalent compounds?

scZoUnD [109]

B. They may be gases, liquids, or solids at room temp.

4 0

3 years ago

Read 2 more answers

Consider the genetic cross for absent-mindedness, which is a dominant trait. What is the probability that the offspring of this

4vir4ik [10]

D)100%

Every single one has the dominate gene so all the offspring will get it

I hope that helps!

8 0

3 years ago

Read 2 more answers

Why are tigers and lions able to mate to produce cubs,but those cubs would not be able to go on to produce any off spring

Sveta_85 [38]

Answer:

Tigers and lions able to mate to produce cubs,but those cubs would not be able to go on to produce any off spring because their sex chromosomes do not match.

Explanation:

Tigers and lions mate to produce ligers and tilons but they do not produce viable sperms or egg.
In an organism there are two copies of chromosomes present in the somatic cells.
But in case of sex cells they receive each set from mother and father. which they duplicate and divide during formation of gametes via meiosis.
in such case if the sets are recieved from two different species then after pairing a mismatch will occur in the gene loci.For example, a eye colour gene may correspond to a paw length gene.
Thus the gametes when produced will not be viable.

4 0

3 years ago

How many grams of KBr is required to prepare 100 mL of<br> 2.0 M KBr solution?

sesenic [268]

Answer:

23.8g

Explanation :

Convert 2.0M into mol using mol= concentration x volume

2.0M x 0.1L (convert 100mL to L since the units for M is mol/L)

= 0.2 mol

We can now find grams by using the molar mass of KBr

=119.023 g/mol (Found online) webqc.org

but can be be calculated by using the molecular weight of K and Br found on the periodic table

We can now calculate the grams by using grams=mol x molar mass

119.023g/mol x 0.2mol

= 23.8046 g

=23.8g (rounded to 1decimal place)

4 0

2 years ago