Calculate the mass in cg,of a 5.0L object if the density is 2.8g/mL?

Answer 1

Try converting that density into cg/L:
2.8g/mL * (100cg / 1g) = 280.0 cg/mL
280.0 cg/mL * (1000mL / 1L) = 28000.0 cg/L
= (2.8 x 10^4) cg/L

Now, multiply that to your given 5.0L:
[(2.8 x 10^4) cg/L] * 5.0L = (14.0 x 10^4) cg = (1.4 x 10^5) cg

Answer 2

1L =1000ml so the density can also be written 2.8 kg/L

and 5l have a mass of 5*2.8 =14kg

1kg = 10^5 cg

5l have a mass 14*10^5 cg