Solve the problem. express your answer to the correct number of significant figures. 6.221 × 7.11 − 13.7 =

6.221 × 7.11 − 13.7

first we determine the product of 6.221 and 7.11 and round the value to minimum number of significant figures which is "3"   since  7.11 has "3" significant figures and 6.221 has "4" significant figures

so Product = 6.221 × 7.11 = 44.2

now we do the subtraction , and round the answer to minimum decimal number

44.2 - 13.7

30.5  

1. 1 mole of anything contains 6.022x10^23 pieces  

d  

2. a  

3. c, number  

5. 1.24x10^24atoms / 6.022x10^23atoms/mole = 2moles h2 atoms  

6. fe2br3 mass = 2moles x mass fe + 3 moles x mass br  

molar mass = grams / number of moles = g/mole  

to find moles = g / molar mass  

to find mass = g = molar mass / moles

dynamic equilibrium is the answer.