//span[contains(@class, 'myclass') and text() = 'qwerty']
or
//span[contains(@class, 'myclass') and normalize-space(text()) = 'qwerty']
//span[contains(@class, 'myclass') and text() = 'qwerty']
or
//span[contains(@class, 'myclass') and normalize-space(text()) = 'qwerty']