user52815: I'm using Blockchain.info's api:
https://blockchain.info/api/blockchain_api
I understand that it is impossible for a transaction to know which block it will be included in but maybe one could use the block height to match the tx to the block? 

user51948: 
but maybe one could use the block height to match the tx to the block?

Indeed that would work fine, block_height is returned by the /rawtx/ call (https://blockchain.info/rawtx/$tx_hash) for transactions that have been included in a block (unconfirmed transactions have no block_height key). Then you can find the block hash and/or information about the block with the /block-height/ call (https://blockchain.info/block-height/$block_height?format=json)

52815: <p>I'm using Blockchain.info's api:</p>

<p><a href="https://blockchain.info/api/blockchain_api" rel="nofollow noreferrer">https://blockchain.info/api/blockchain_api</a></p>

<p>I understand that it is impossible for a transaction to know which block it will be included in but maybe one could use the block height to match the tx to the block? </p>
 51948: <blockquote>
  <p>but maybe one could use the block height to match the tx to the block?</p>
</blockquote>

<p>Indeed that would work fine, <code>block_height</code> is returned by the /rawtx/ call (<a href="https://blockchain.info/rawtx/" rel="nofollow noreferrer">https://blockchain.info/rawtx/</a>$tx_hash) for transactions that have been included in a block (unconfirmed transactions have no block_height key). Then you can find the block hash and/or information about the block with the /block-height/ call (<a href="https://blockchain.info/block-height/" rel="nofollow noreferrer">https://blockchain.info/block-height/</a>$block_height?format=json)</p>
