calculate the mass given element of each of the following compounds

a) brimine in 50.0 potassium bromide, KBr
b) Chromium in 1.00 kg sodium dichromate Na2Cr2O7

Here is how to do (a). You can do (b) the same way.

The molar mass of KBr is 39.1 + 79.9 = 119.0. I just added the atomic masses of one K and one Br atom.
50.0 g is 50.0/119.0 = 0.420 moles.
The mass of bromine is the sample is 79.9 g/mole* 0.420 moles = 33.6 g

a) Well, bromine is the element we're interested in, so let's focus on that. In potassium bromide, the chemical formula tells us that there is one bromine atom for each KBr unit. To calculate the mass of bromine in 50.0 grams of KBr, we need to know the molar mass of bromine, which is approximately 79.90 grams/mol. So, we can set up a simple proportion:

(1 mol KBr / 1 mol Br) x (79.90 g Br / 1 mol Br) x (50.0 g KBr) = mass of bromine in 50.0 g KBr.

Now, let's solve this math equation together. It seems like we need a serious bromance to find the answer, don't you think?

b) Oh boy, a kilogram! That's quite big. But fear not, Clown Bot is here to help. The chemical formula for sodium dichromate is Na2Cr2O7, so we're interested in the mass of chromium. To calculate the mass of chromium in 1.00 kg of Na2Cr2O7, we'll need the molar mass of chromium, which is approximately 52.00 g/mol.

Now, let's get cracking! To solve this, we can set up a proportion:

(1 mol Na2Cr2O7 / 2 mol Cr) x (52.00 g Cr / 1 mol Cr) x (1.00 kg Na2Cr2O7) = mass of chromium in 1.00 kg Na2Cr2O7.

Alright, let's crunch those numbers and see what we get. Just remember, this equation might be serious, but it won't make you chromophobic!

To calculate the mass of an element in a compound, you need to know the molar mass of the compound and the molar mass of the element.

a) Potassium Bromide (KBr):
1. Find the molar mass of KBr:
- Molar mass of K = 39.10 g/mol
- Molar mass of Br = 79.90 g/mol
- Molar mass of KBr = (39.10 g/mol) + (79.90 g/mol) = 119.00 g/mol

2. Calculate the mass of bromine in 50.0 grams of KBr:
- Mass of Br = (Molar mass of Br / Molar mass of KBr) x Mass of KBr
- Mass of Br = (79.90 g/mol / 119.00 g/mol) x 50.0 g
- Mass of Br = 33.70 g

Therefore, the mass of bromine in 50.0 g of potassium bromide is 33.70 g.

b) Sodium Dichromate (Na2Cr2O7):
1. Find the molar mass of Na2Cr2O7:
- Molar mass of Na = 22.99 g/mol
- Molar mass of Cr = 52.00 g/mol
- Molar mass of O = 16.00 g/mol
- Molar mass of Na2Cr2O7 = (2 x 22.99 g/mol) + (2 x 52.00 g/mol) + (7 x 16.00 g/mol) = 294.00 g/mol

2. Calculate the mass of chromium in 1.00 kg of Na2Cr2O7:
- Mass of Cr = (Molar mass of Cr / Molar mass of Na2Cr2O7) x Mass of Na2Cr2O7
- Mass of Cr = (52.00 g/mol / 294.00 g/mol) x 1000.0 g
- Mass of Cr = 176.87 g

Therefore, the mass of chromium in 1.00 kg of sodium dichromate is 176.87 g.

To calculate the mass of a specific element in a compound, you need to know the molar mass of the compound and the atomic mass of the element.

a) To find the mass of bromine (Br) in 50.0 g of potassium bromide (KBr), you need to follow these steps:
1. Find the molar mass of KBr by summing the atomic masses of each element in the compound:
- Atomic mass of K (potassium) = 39.10 g/mol
- Atomic mass of Br (bromine) = 79.90 g/mol
- Molar mass of KBr = atomic mass of K + atomic mass of Br = 39.10 g/mol + 79.90 g/mol = 119.00 g/mol

2. Calculate the moles of KBr in 50.0 g by using the formula:
Moles = Mass (g) / Molar mass (g/mol)
Moles of KBr = 50.0 g / 119.00 g/mol ≈ 0.420 moles

3. Since the atomic mass of Br is 79.90 g/mol, the mass of bromine in 0.420 moles of KBr can be calculated by multiplying the moles of KBr by the atomic mass of Br:
Mass of bromine = Moles of KBr * Atomic mass of Br
Mass of bromine = 0.420 moles * 79.90 g/mol ≈ 33.57 g

So, the mass of bromine in 50.0 g of potassium bromide is approximately 33.57 g.

b) To find the mass of chromium (Cr) in 1.00 kg of sodium dichromate (Na2Cr2O7), you need to follow a similar method:
1. Find the molar mass of Na2Cr2O7 by summing the atomic masses of each element in the compound:
- Atomic mass of Na (sodium) = 22.99 g/mol
- Atomic mass of Cr (chromium) = 52.00 g/mol
- Atomic mass of O (oxygen) = 16.00 g/mol (there are seven oxygen atoms in Na2Cr2O7)
- Molar mass of Na2Cr2O7 = (2 * atomic mass of Na) + (2 * atomic mass of Cr) + (7 * atomic mass of O)
= (2 * 22.99 g/mol) + (2 * 52.00 g/mol) + (7 * 16.00 g/mol)
= 22.99 g/mol + 104.00 g/mol + 112.00 g/mol
= 238.99 g/mol

2. Calculate the moles of Na2Cr2O7 in 1.00 kg by using the formula:
Moles = Mass (g) / Molar mass (g/mol)
Moles of Na2Cr2O7 = 1000 g / 238.99 g/mol ≈ 4.184 moles

3. Since the atomic mass of Cr is 52.00 g/mol, the mass of chromium in 4.184 moles of Na2Cr2O7 can be calculated by multiplying the moles of Na2Cr2O7 by the atomic mass of Cr:
Mass of chromium = Moles of Na2Cr2O7 * Atomic mass of Cr
Mass of chromium = 4.184 moles * 52.00 g/mol ≈ 217.57 g

So, the mass of chromium in 1.00 kg of sodium dichromate is approximately 217.57 g.