Question

1.A chemist requires 0.240 mol Na2CO3 for a reaction. How many grams does this correspond to? 2.How many grams of potassium oxide (K2O) are there in 0.502 moles? 3.How many moles of carbon monoxide (CO) are in 18.3 g of the compound? 4.How many atoms are there in 80.3 g of potassium dihydrogen phosphate (KH2PO4)? 4.A sample of C3H8 has 9.52 × 1024 H atoms. How many carbon atoms does the sample contain and What is the total mass of the sample?

Answer 1

1.A chemist requires 0.240 mol Na2CO3 for a reaction. How many grams does this correspond to?

Amount in g = number of moles * molar mass

= 0.240 mol Na2CO3 *105.9884 g/mol

= 25.44 g Na2CO3

2.How many grams of potassium oxide (K2O) are there in 0.502 moles?

Amount in g = number of moles * molar mass

= 0.502 mol K2O * 94.196 g/mol

= 47.29 g K2O

3.How many moles of carbon monoxide (CO) are in 18.3 g of the compound?

Number of moles = amount in g/ molar mass

= 18.3 g CO/ 28.01 g/ mole

= 0.653 moles CO

4.How many atoms are there in 80.3 g of potassium dihydrogen phosphate (KH2PO4)?

Number of moles = amount in g/ molar mass

= 80.3 g KH2PO4/ 136.086g/ mole

= 0.59 moles KH2PO4

1 Mole = 6.023 *10^23 molecules

0.59 moles KH2PO4 = 3.55*10^23 molecules

1 molecule of KH2PO4 =there are 8 atom

1 K, 2 H 1 P 4 O

Thus 3.55*10^23 molecules of KH2PO4 = 8 * 3.55*10^23

= 2.84*10^24 atoms