19. Why should all measurements be done multiple times?

Increasing precision with multiple measurements

Explanation:

The more measurements you take (provided there is no problem with the clock!), the better your estimate will be. Taking multiple measurements also allows you to better estimate the uncertainty in your measurements by checking how reproducible the measurements are.

65.2%

Explanation:

It is given that :

Therefore, 60 g of nitrogen oxide will produce 92 g of nitrogen dioxide

or 60 kg of nitrogen oxide will produce 92 kg of nitrogen dioxide

or 1500 kg of nitrogen oxide will produce of nitrogen dioxide

Therefore the percentage yield = (Actual yield / Expected yield) x 100

percentage yield =

Percentage yield = 65.217 %