Is there likely to be any mental impairment to offspring of one parent with adhd?

See below. Adhd tends to be seen within families. However, the child is not at any increased risk for any type of "mental impairment".
Not sure of question. Adhd runs in families, so having a parent with adhd increases your odds of having adhd. Some other disorders such as anxiety and depression also may be more likely in a family with an adhd parent. However, overall brain function is not affected by adhd, if that is the concern. Iq in those with adhd is basically the same as for those without adhd.