Final answer:
There are two significant figures in 0.00000090 g of copper. This is determined by excluding the leading zeros, which are not significant, leaving the '9' and the trailing '0' as the significant figures.
Step-by-step explanation:
In chemistry, significant figures are crucial for representing the precision of a measurement. The number of significant figures in 0.00000090 g of copper is determined by looking at the digits that provide meaningful contribution to its measurement precision. Following the rules for significant figures, leading zeros do not count as significant; thus, the significant digits are the '9' and the last '0'. Therefore, there are two significant figures in this measurement, which corresponds to option B.
Let's apply this knowledge to other examples:
- 0.0009 has one significant figure ('9').
- 15,450.0 has six significant figures (all numbers plus the trailing zero after the decimal are significant).
- 6x10³ is in scientific notation and has one significant figure ('6').
- 87.990 has five significant figures (all numbers including the trailing zeros).
- 30.42 has four significant figures (all numbers).