Purchasing power of currency abroad
Well in principle you could. Let's suppose there are two countries that do not trade a lot. Then even if their economic growth is relatively similar, we should not expect their exchange rate to be 1:1. 

The exchange rate is a price, so if country A likes more the goods and services from country B than vice-versa, you should expect currency B to have a larger purchasing power than currency A. 

However, The demand for goods from abroad is correlated with income, so if both countries have relatively similar economic growths, and they trade a lot with each other, the relative purchasing power of their currencies will tend to be similar.