# please check my answers. THANK YOU.

1) The percent by mass of carbon in acetone, C3H6O is.

Answer: 62.1%

2) What is the percent by mass of zinc, Zn, in ZnCO3?

Answer: 52.3%

3)What is the percentage of water in the compound BaCl2 * 2H2O?

Answer: 7.96%

4)How many atoms are in one mole of NO2?

Answer: 2.77 x 10^25

I looked on a "calculator" on the internet to help and they list 64.04% for C, 52.15% for Zn 14.74% for H2O (don't forget to multiply by 2 for mols H2O). 1 mol NO2 contains 3 atoms; therefore, 1 mol will contain 3 x 6.022 x 10^23 atoms. You don't say to what accuracy the percents should be known but i suspect your numbers are ok when rounded off (except for 3.)

My only options for numbers 1-3 are...

1. a) 20.7% b) 62.1% c) 1.61% d) 30.0%

2. a) 20.0% b) 47.7% c) 52.3% d) 65.4%

3. a) 33.3% b) 17.3% c) 7.96% d) 14.8%

1 is ok.

2 is ok.

3. BaCl2.2H2O

I will approximate.

Ba = 137.3

Cl = 35.5 x 2 = 71

H2O = 16 + 2 = 18 and 18 x 2 = 36

Total is 244.3

Then %H2O = (36/244.3) x 100 = 14.7% so I would pick d.

## 1) To calculate the percent by mass of carbon in acetone, C3H6O, you need to find the mass of carbon in the compound and divide it by the total mass of the compound.

The molar mass of carbon (C) is 12.01 g/mol, and there are three carbon atoms in C3H6O. The molar mass of acetone (C3H6O) is 58.08 g/mol.

The mass of carbon in one mole of acetone is 3 atoms x 12.01 g/mol = 36.03 g/mol.

To find the percent by mass, divide the mass of carbon by the molar mass of acetone and multiply by 100:

(36.03 g/mol / 58.08 g/mol) x 100% = 62.1%

So, the answer is 62.1%.

2) To find the percent by mass of zinc (Zn) in ZnCO3, you need to calculate the mass of zinc in the compound and divide it by the total mass of the compound.

The molar mass of zinc (Zn) is 65.38 g/mol. The molar mass of ZnCO3 is 125.38 g/mol (Zn = 65.38 g/mol + C = 12.01 g/mol + O = 16.00 g/mol x 3).

The mass of zinc in one mole of ZnCO3 is 65.38 g/mol.

To find the percent by mass, divide the mass of zinc by the molar mass of ZnCO3 and multiply by 100:

(65.38 g/mol / 125.38 g/mol) x 100% = 52.3%

So, the answer is 52.3%.

3) To find the percentage of water in the compound BaCl2 * 2H2O, you need to calculate the mass of water in the compound and divide it by the total mass of the compound.

The molar mass of water (H2O) is 18.02 g/mol. The molar mass of BaCl2 is 208.23 g/mol (Ba = 137.33 g/mol + Cl = 35.46 g/mol x 2).

The mass of water in one mole of BaCl2 * 2H2O is 2 x (18.02 g/mol) = 36.04 g/mol.

To find the percentage of water, divide the mass of water by the total mass of BaCl2 * 2H2O and multiply by 100:

(36.04 g/mol / 244.27 g/mol) x 100% = 14.77% (rounded to 2 decimal places)

So, the answer is approximately 14.77%. Based on the given options, the closest answer is 14.8% (option d).

4) For the question of how many atoms are in one mole of NO2, you need to know the number of atoms present in one molecule of NO2.

The formula for NO2 indicates there is one nitrogen (N) atom and two oxygen (O) atoms in one molecule of NO2.

According to Avogadro's number (6.022 x 10^23 atoms/mol), one mole of any substance contains 6.022 x 10^23 entities. Therefore, in one mole of NO2, there are 2 (oxygen atoms per NO2 molecule) x 6.022 x 10^23 (Avogadro's number) = 1.2044 x 10^24 oxygen atoms.

So, the number of atoms in one mole of NO2 is 1.2044 x 10^24. However, the given answer of 2.77 x 10^25 is different. It is possible that this answer is considering the total number of atoms, including both nitrogen and oxygen, or it may contain a rounding error. Without further information, it is difficult to determine the accuracy of the given answer.